MAIN Index



~ Sea Divers ~

Security Notes to assist "Divers" in respect of Surface Air Supplies and more:

Compressed Air Contamination -- Air Intake filter & noxious gases -- Oils for compressors -- Cooling for compressors -- Compressor capacity under load. -- Heat & water condensate -- Bacteria contamination due to moisture -- Activated carbon's capacity to cleanse fumes -- capacity to dry out air -- Filtration of - Water - oil - Air -- Air hose sizes -- Pressure differential, air - water --"Mental" capacity to rationalise irrationality under stress. Hypoventilation through fear or trauma causing death.

Tim's Safety Alert - Tim's 4 stage safety filter.



Compressed air contamination results from either contaminated air entering the compressor intake (dust or hydrocarbons from exhaust and/or other fumes), or from oil contamination during compression pumping. It also occurs after compression through air receivers contaminated by rust, bacterial growth, stale air, & dangerous Carbon Monoxide (CO) forming from overheated oil.

The air intake delivery line needs be of a diameter at least three times that of the outlet air or more if there is a long intake extension line fitted. The intake filter needs be protected against the weather (water ingress), it needs be checked prior to each dive for free flow and free from water or other restrictions.

A 1-2 micron filter of adequate size is recommended for the air intake filter. Car filter inserts are cheap to purchase, readily available, adequate of size, and of 2 micron. The air intake filter needs be placed as far as possible from the petrol driven motor exhaust to ensure that wind gusts do not allow exhaust gases to be drawn in.

Also, the intake point must be well above any place in the boat in which carbon monoxide or gas from gas cylinders could collect, as noxious gases are heavier than air. i.e. place the intake above the level of the sides of the boat as well as above the height of the motor exhaust.

~ Compressor lubrication ~  

For your information I give extracts from a letter received by me from Brad Dawson of Castrol Australia dated 4.4.96 ... Quote -

Vegetable oils are not suitable for high temperature applications (eg compressors) as they oxidise readily at above 70-80 degree C. A compressor using vegetable oil would quickly become choked with deposits.......The benefits of using a dedicated compressor oil are:

Better resistance to high temperature oxidation and better water separation (demulsibility)........

The main factors influencing oil consumption are viscosity and volatility........Synthetics have by far the lowest volatility (evaporation) level........Synthetics give by far the best performance due to low consumption and up to 5 times the service life .........

The additive levels of compressor oils are very low (compared to engine oil)..... with typical additive contents less than 5%.......... all additives are toxic. The maximum operating temperatures would be as follows:

Vegetable - up to 60-70 degrees, mineral - up to 90 degrees. Synthetics can operate consistently above 100 degree C without any problems..... unquote.

The synthetic oil is the best lubricator in rotary compressors, and gives the lowest carry-over of oil into the air delivered. Remember, to only use a "dedicated" compressor oil as this is an oil that is specifically designed for air compressor lubrication. Compression of air can result in high air/oil temperatures.

As compressors are not internal combustion motors, they are free of contaminants resulting from internal combustion, and thus the dedicated oils used are more free of dangerous additives.

Also, some people use non-dedicated compressor oils merely because they have a high flash point, meaning that they can run hotter before "burning" which releases fatal gases. A high flash point oil does not necessarily mean that it is a good lubricator, eg: hydraulic oils.

The use of a non-dedicated compressor oil probably means you may be using an oil having either excess additives, or as in medicinal oils such as Ondina, no antioxidants, and thus one that may also run hotter if it is not a good "lubricator," thus wearing out your air pump quicker, with the further consequence of allowing up to ten times more oil vapour into the airflow through overheated & worn cylinder barrels.

This increases filtration demands and also the danger to divers if the filtration is inadequate or used in excess between changes.

For many years people have been using medicinal oils. These oils have no antioxidants, thus they "break down" due to hot oil interaction with the water in the air, resulting in poor lubrication and the formation of dangerous CO gases during partial vapour burning.

Shell recommend to ONLY use 'Corena P 100 grade' oil in piston compressors.

~ Operational Cooling of compressors ~

Most small air compressors (under 75 kg weight of around 8 to 50 cu'/min) that are commonly used by "Hookah" divers are not designed for continuous "on line" pressure operation. They are designed for a 60/40 combination.

This means that they are designed to pump-up the receiver and then cut off. This "off" time under no load (freewheeling) allows them to cool, and as air consumption takes place, they switch on/cut-in again automatically as the pressure drops.

As diving operations often use petrol driven motors that are required to run continuously, it is important to only use a compressor/motor unit that has the capacity to deliver double the maximum air supply needed. This will allow the compressor to cycle in "free wheel" mode for a time after it has pumped-up the air receiver tank.

This "rest cooling time" requires the use of a "Genii" or similar pressure operated valve that shuts off the pressurised air line to the tanks, and vents the cycling air to atmosphere, thus allowing the pump to have an un-pressurised free airflow through it that cools it. To this unit can also be attached a throttle control that slows the drive unit/motor down to 'idle,' conserving fuel and minimising wear to "driver & driven." And easier on the "deckie's" ears.

As the air receiver pressure drops, the throttle opens and the pressurised supply reactivates to pump up the air tanks again. The larger the air storage, the longer the "unit" rests between pumping up mode and better cooling occurs. As the compressor now runs much cooler, wear is reduced, the compressor runs more efficiently (air delivered) and there is far less chance of oil carry-over in the airflow from heated gases being generated.

~ Operational compressor air requirement ~.

It is recommended that doubling the total max depth air requirement figure be used in calculating air compressor delivery required for maximum optimum safe supply to diver/s. Taking into account that at each additional 30' depth, the air needed through pressure depth increase is an additional atmosphere for each diver, eg:

One diver air per minute at sea level needs 30 L/min (As 1 cu' min = 28.4L) Therefore compressor capacity needed is:

@ 30' = 60L/min approx
@ 60' = 90L/min approx-
@ 90' = 120L/min approx
@ 120' = 150L/min approx

If you feel you need "more" air per minute than this table, use your figures.

As a compressor needs to run on 60/40 basis, it means it must be "off" 40% of operating time ( free wheeling with nil load pressure ) to ensure adequate oil & unit cooling and maintaining a safe standard of operation.

Thus a compressor needing to supply the above 150L/min during its 60% "on load delivery" capacity cycle, needs to be able to have a 100% capacity supply of approx 250 L/min for a single diver operation at the above max depth of 120'. Doubling the 150L needed, gives a compressor requirement output under load of 300L/min.

Two divers working at max depth of 30' using 60L/min each = 120L/min, need the following: 120L x 2. = compressor air delivery capacity of 200 - 240L/min.

Two divers working at max depth of 90' using 120L/min each = 240L/min, need the following: 240L x 2. = compressor air delivery capacity of 400 - 480L/min.

With the 50% additional capacity, the compressor is being given an adequate "off load time" slightly above manufactures specification of 40%, and thus giving more "leeway" for underwater safety. You choose your "safety %" requirement.

A compressor free running (not under load) @ 1400 rpm that delivers 22/cu/'min from its "swept unloaded volume," may only deliver 11.5 cu'/min under load at 100psi pressure, being some 320 L/min. that is only half of the "advertised" free of pressure air swept volume capacity at a given revolution. Showing that we need to ensure our air pump has adequate capacity under pressure & at depth, when divers may breath faster and require more/faster air delivery.

Compressors can be "speeded-up" to give additional air volume, but it is surely wisest to stay within the manufacturers recommendation, and design your unit to meet your need with quality capacity and power to spare, rather than struggle with an under capacity unit being stretched beyond its mechanical and your biological limit.

~ Filtration of Air - water and oil ~

The air filtration has been spoken of ref: air filter prior to compression. Air has the capacity to carry free water. Free water condensation takes place when air cools from expansion when changing to a lower pressure, as well as when warm air is met by a colder situation, being another air mass or material.

During compression, air temperature is heated considerably higher than the ambient (outside) temperature. The compressed and heated air flow is then constrained by the very pipe along which it is travelling, until it enters an area where it can expand, the expansion causes it to cool rapidly and water condensate forms.

Thus, any type of filter is an expansion chamber that can permit water condensation to occur. If there is adequate cooling in the after piping prior to reaching the filter, then the amount of water condensate is lessened.

Hence the need for a compressor to have not only a fan type pulley that itself keeps the cylinder head and compressed air as cool as possible, but the compressed air needs to be cooled with the aid of a water coil over the side of the boat, lowering it to 10 degrees below ambient if possible, prior to filtration.

Wet air or dry air ? - the air that we breathe is natural, moist and soothing to throat and lungs, and if dried out too much, we would suffer respiratory problems. Air being compressed will by this very cooling after expansion process dry it out to a point drier that when it entered the compressor. "How dry" is dry enough to filter it of its impurities, and "why dry" at all?

Moist air causes metal cylinders to rust. Diving tanks and storage air receivers have for many years been of mild steel, as have air receivers in compression charging facilities. To minimise the problem of rust contamination of these cylinders and air tools etc, "agencies" do their best to supply "dry air," not considering the unnatural implications for the "breather."

Certainly water carrying oil vapour needs be separated as does the oil as much as possible prior to final filtering. If it was not, then the absorption capacity of the final filter pads & activated charcoal would not last long.

~ Activated charcoal - carbon ~

Activated charcoal/carbon is manufactured from Wood, coal, peat, or coconut husk. It is "activated" by heating it in nitrogen, this opens up the pores, resulting in a highly filtration medium. The hardest and best, and the best resistant to breaking down into dust is the coconut fibre. There are different grades and sizes.

A particle grade of not less than .5 mm up to 3mm mixed to give a good solid mass is recommended. Maximum gas vapour absorption as used in gas masks by armed forces is the Pica brand TE 90 (.5mm-1.7mm gran) and TE 50 (1-3mm). This is available in bulk from Carbon products of Australia.

Activated charcoal can be, and is used in industry to "trap" and filter out oils, waxes and other "heavy" substances. It can and does filter toxins even when saturated by water, ie: the cleansing filters used in fish tanks. So a little moisture in the air or carbon will not effect the carbon to the extent that it cannot filter.

It is but a matter of "how much" carbon is used, and very importantly "how slowly" does the air flow through the carbon filter, too fast, and the filtration can be nil, too slow or slowly, and you are 101 + % safe. How good is your filter ?? Manufacturers may state "7 cu'/min flow" etc, but what if you are using more air ? how much is the filtering process diminished, 10% or 90% ?.

Manufacturers are cautious about how many cu' air can be filtered before changes are needed. Why use an expensive filter cartridge having relatively small amounts of carbon, and lots of expensive plastic holder, when you can charge your own everlasting filter contents & pads for $ 5 that contains 4 times more carbon.! A narrow bodied filter maintains a fast air flow through it, less time for air/carbon contact. A wide bodied filter can "hold" the passing air contact 10 times longer, assuring a good cleanse. Carbon monoxide & dioxide is not filtered by activated charcoal.

Activated carbon has the capacity to "draw out" large amounts of moisture from the passing air, causing the air to become excessively dry. This can be avoided by soaking the carbon granules in clean rainwater over night, and drip drying them out for an hour on a piece of newspaper before loading. If they are too moist, the passing air flow will "dry them," if they are too dry, they will absorb passing moisture until "saturated." Washing and loading with slightly moist carbon eliminates carbon dust from the system, and ensures a "natural" moistness .

Having the filter mounted apart from the vibrating machinery is best, as it eliminates carbon particle "break down" and powdering. The "Tim's" Div-Air purification system has a fourth dynamic centrifugal filter between carbon filter and diver to catch any carbon particles that may pass the carbon filter due to faulty loading by the diver.

Do not be concerned with "cloudy" water vapour appearing in your face mask, the air flowing down the air hose is cooling, and as it passes through the small constriction of the regulator, it not only speeds up slightly, but during expansion into the mouthpiece, it suffers a pressure drop and condenses. No more dangerous to you than the water vapour in the shower.

Certainly, "wet" conditions in the system may allow bacteria to breed. But a filter that is used or unused for a long time is also able to be contaminated, as are air receivers that are made out of mild steel, that soon become full of rust and dirty water, that will daily contaminate any air flow passing through.

The safest way is to be able to frequently charge your own filter contents. This way, when not in use, you can also leave it clean and empty.

Any system having all its air filters placed before it goes into the air storage receiver is not adequately protecting the diver.

Final activated carbon & filter pads filtration should take place when the air exits the storage chamber. This will ensure that any contamination from rust etc is also cleansed in the final filtering.

The only thing between the final filtration and diver should be the air delivery hose. If your system has a very large storage chamber that is left unused for any length of time, then it should be disconnected from the final filter and purged with fresh air before reconnecting and use.

Most filtration systems rely on the use of replaceable cartridges and foam covers to filter oil and particles prior to carbon filtering. Any system that "catches" oil and requires the 'following" passing air to flow through that contaminated medium is in itself a contaminator if it is not replaced frequently.

~ "Tim's" diving units ~

Tim's diving filtration units are of stainless steel. The filtration system combines "dynamic" filtration of water & oil in stainless steel cylinders. This method does not use cartridges or foam screens, but centrifugal and increased air speed impact methods of extraction that are very efficient. Due to this, the following on-going airflow does not need to pass through previously collected wastes that "fell away."

The activated carbon filter has been designed to be easily removable and "upended," so as to load from the bottom, having a perforated mesh screen welded on the top end. Spring loaded underneath. Thus, no matter how much pressure of air is given, the felt pad and its contents cannot be dislodged. The airflow will only add to the compacting of the filter contents.

As the air leaves this charcoal filter, it passes through a centrifugal safety filter. In the event that the diver or operator loaded the felt pad incorrectly, allowing activated charcoal granules to flow past, they would all be trapped and separated out of the air flow in this safety filter.

The "Tim's" filters can monthly or as often as desired, be washed out and maintained in a totally clean state at no cost to the user. The only on-going cost is the activated carbon & filter pads in the final filter.

The stainless steel "Tim's" carbon filter has a "body width" of 2.5" and is 4" long. Containing some 200 gm of activated carbon. This filter is removable and the contents changed in a couple of minutes. Thus it is easy to maintain good quality purified air at all times.

To avoid any bacterial contamination of divers lungs through the system, both the filters and air receivers can be 'flooded" with a water solution containing .05% Chlorhexidine (3 mil to 4 litres water approx), and left standing full for half an hour before draining and flushing again.

This ensures the destruction of a wide range of bacteria, thus ensuring that the entire airflow direct to diver is kept pure. Done a regularly monthly or as desired basis. The "mouthpiece" may be rinsed daily after use.

Remember, it is not just the filters that filter the passing air. Any surface including hoses, filter and cylinder walls "pick up" contamination over time as air flows past. Thus a good occasional submerge in detergent, and/or total hose renewal is recommended.

~ Flooding of filter systems ~

Many filter systems today are designed mainly for "on ground" operation, meaning that they supply air to one or more operators working at one atmosphere, breathing more shallowly than a diver, and also the filtration system is on "stable ground."

Water operation is "unstable ground," in that there is constant movement from both the vessel, as well as vibration from the "Hookah" drive motor if the filters are attached to the frame. Further to this, Many "modern" filters have an "automatic" self draining unit at the lower end of the filter housing. These types of drains need a clean product to continue to function properly, or they can block up during use.

As stated before, many air receiver containers are of mild steel, some mild steel unit "frames" are even used as the primary air receiver. It has also been stated that water separation should take place before the air enters the air receiver.

If this does not occur, then not only does a lot of water collect in the "frame" or receiver (up to 1 Litre per 5 hour operation), but it is "wallowing around" in rusty muck, and as the boat "rocks," a sudden mass volume of water can be forced in one "swoop" into the filtration system, totally engulfing it.

This can also easily occur if you have "plug in" connectors on your diving hose. If your hose is connected before starting up and pressurising the whole system, then as air is rising in pressure, the whole system slowly fills up, and air flows slowly through your carbon filter as it enters your diving hose to equalise all the pressure.

If your hose is not connected, and you have "plug in" connectors, there is a totally different unseen scenario. 100 metres of 10 mm hose can hold 7.8 L of air at 1 Atmos. If your system has been pressurised to 120 psi (8 Atmos), then when a hose is "plugged-in," 7.8 x 8 Bar = 60 litres of air will in an instant "swoosh" through the filtration system.

As you "connect" your hose, this incredible "surge" of pressurised air will accelerate instantly through your filter system, most carbon filters cannot properly cleanse this instant volume of air, and it may allow contamination through to the diver or cause partial or total flooding of filters in an "unclean" system. Both occurrences are very undesirable.

Make sure your hose is connected before pressurising the system. If you wish to "purge" the unit first, then do so without the hose connected, and drop the pressure in the entire system before reconnecting. Fast "bleeding" or depressurising the system should be done at the air receiver and not from the exit side of the carbon filter.

It is not commonly realised how quickly we just "assume" that an automatic operation is functioning properly. ie. An automatic filter drain is working to its full capacity. I believe that the use of a manual drain cock is better. This ensures that we daily learn to check it as we manually drain it.

The water filter housing needs be large enough to accommodate the water collected. It is also possible to have the manual valve open a crack, so "direct air " under pressure keeps water draining continually. How often do you look into your filters,? most filter "bodies" are sealed and thus internal water contamination is unseen.

~ Air delivery hoses ~

When a hose has no airflow passing along it, the whole hose volume is 'static" with a balanced pressure, ie; 120 psi. As soon as one end is "opened' as occurs when breathing in, there is a pressure drop at this point, and the whole air mass in the pipe flows along its length to "take up" the drop in pressure. The rate of flow and its volume in feet per second depend on the pressure as well as the diameter of the pipe.

The smaller the hose diameter, and the longer its length, the more "pressure loss" and "air delivery delay" to diver results due to friction. This pressure loss causes a "slow down" of the air flow as it commences to move from a standstill when you breath in.

This has the effect of restricting the volume of passing air to the diver at the "moment" of inhaling. An adequate volume means that you are "comfortable," any lack in volume results in a negative "suck" on the divers part, leading to distress.

The area of a "hole in the pipe," its circle area, is as follows: 3.14 x radius squared.

8 mm air delivery hose - 3.14 x 4 x 4 = 50 mm.
10 mm air delivery hose - 3.14 x 5 x 5 = 78 mm
16 mm air delivery hose - 3.14 x 8 x 8 = 200 mm

The larger the hose internal diameter, the 'easier" the air will flow. If you are finding any difficulty with breathing, then immediately rise up to shallower water. The fault may be one of many causes. But it is for sure the direct result of a lack of necessary volume of air to you personally at the depth of your dive operation.

The fault may be a compressor that has not got the capacity to deliver the additional air volume needed as you go deeper. It may be that the filter system is blocked. Or it may be that your air line cannot accommodate the extra volume of air flow needed. If you are "sharing" the same feeder line, you need an adequate volume of air.

~ The 'instant air' receiver ~

The "Tim's" system incorporates an IA Receiver,( Instant Air Receiver). This is only a small half litre cylinder (2.5" x 8") strapped around the waist on a belt. The air pipe enters on one end, and the regulator pipe exits the other. As the "inner" air pressure is equal to the compressor 120 psi, the actual air volume in the IA receiver is .5 x 8 bar = 4 Litres @ 120 psi.

If your present system is in any way lacking flow volume at depth or with two divers breathing in at the same moment, this IA unit ensures that at all times there is a lung full of air ready to be drawn in with no delivery delay.

This is due to the dynamics of air, in that in your present system, as you are in the mode of exhaling air, the air flow in the pipe becomes "stationary," or in a "slow" supply flow if it is still "filling up" the pipe after your last gasp for air.! Your compressor may have the necessary air "Volume" production, but delivery delay through small hoses could effect its "down pipe" flow rate.

The longer and thinner the hose, the slower the air flows. The Pressure loss may be 5 psi or more, and a 100 metre length of 8 mm hose will have an air flow restriction many times more than a 16 mm dia. hose of equal length.

With an IA receiver, the air volume needed for your next breath is still able to be flowing in and made ready in "bulk" during the time you are holding a breath of air or exhaling air. The time when in most systems the "down pipe" airflow is at a standstill.

This also applies to a two diver process. It means that you both have a fully available unrestricted inhale that is not dependent on slow moving air needing to travel down 10 feet of hose before reaching your chest cavity.

IF you find a situation that due to "total" lack of compressor delivery capacity, or blocked filtration, then obviously, even an IA receiver is not going to assist you.

The IA receiver is a unit that compensates for air flow loss down an air delivery pipe. It ensures that there is NO delay demand or volume restriction supply in times of great air volume need. Divers need to ensure they understand the capacity of the unit they use and its limitations as well as their own. The greatest danger to any diver is their own MIND.

IF your thoughts let you down - ahead you will frown, or maybe even drown!

~ Pressure differential ~

Pressure differential. How does this effect you ? Other than the well documented known effects of changes that take place in the human body due to depth, time immersed, and gases inhaled, that you should be familiar with, there is another basic need. The need to be able to "draw in" an unrestricted volume of air at whatever depth you are operating.

What effects this.? We have discussed compressor output capacity under load (increasing in volume requirement) the deeper you go, and flow pressure/volume loss due to friction in the air delivery hose. The other factor, is relative to the pressure differential between the air pressure being delivered to your demand valve, and the pressure on you from the water that surrounds you.

We stand on earth with a pressure of one "Atmosphere," or one "Bar." of 14.7 psi. It is a "balanced" pressure to us (within & without) when the muscles in our chest are "relaxed." Any muscular action that "raises" the chest cavity permits a "partial" vacuum (lowering of pressure) due to the immediate pressure differential created, thus the outside air flows in.

The pressure drop that our muscles can create on inhaling are about minus 1-2 psi. The muscular force that we can generate on the exhale by muscular compression of our chest is much greater, 7 psi and more. If we only need a 2 psi "pressure differential" to breath in, why do we need such high in line pressures, 100 psi or more.? Because, these pressures are not only to accommodate the 2 psi pressure differential needed to breathe, but are needed to compensate for the increase of the outside water pressure that increases the deeper we go.

Air pressure within our lungs increases as we dive deeper, and at all times is "equal" to the outside water pressure. The muscular activity that moves our biological diaphragm opens the "mechanical" demand valve by lowering the pressure in our mouth, at this moment, the "in line" pressure with its "positive pressure differential" flows in. At all times the "in line" air pressure must equal or exceed the pressure of the water at divers depth, or we would not be able to breathe in.

Each foot of water depth increases the "outside" pressure upon your body by .5 lb. Thus at an operational depth of 100,' the water pressure around you is 50 psi. The air pressure in your lungs would also have risen to 50 psi to compensate.

If your air delivery line and air receivers contained a pressure a little above that 50 psi, eg 53 psi, then on breathing in, air would flow into your lungs. However, a slow flow-in, due to a low pressure differential of only 3 psi would put you under stress, as this "initial" 3 psi additional positive pressure would in fact drop, due to line friction flow losses as you tried to breathe in "deeply" through a "straw."!.(thin pipe).

How much "pressure differential" do we need to breath easy. ? If the air delivery hose was a foot wide,! then as on dry ground, zero psi pressure differential would suffice.!

But as divers use hose pipes having 8 - 16 mm internal dia, a far greater pressure differential is needed to overcome the time taken for the air to "accelerate" and "move" when the inhale action is commenced.

Most small compressors deliver up to 120 psi. this is a 70 psi positive pressure differential greater than the water pressure of 50 psi at 100' depth.

Even diving at a depth of 120' you are quite "safe" if your air receiver pressure is "operating" between 80 - 120 psi, as long as your "demands" for air are met. Assuming that your compressor is of adequate air volume capacity, your air demands will be met if you use a hose of adequate diameter for its length.

Remember, that the deeper you dive, the larger the air flow volume your hose will be carrying, and whether there are more than one diver on a single hose, as this too may effect hose choice ...

~ The rational facts of the matter ~

The longer the air line is, the greater the air flow volume loss, due to friction.
The greater the depth of water, the volume of air use increases, maybe x 5 or more.
A long line added to a deep water situation x 2 divers and you need a BIG hose pipe.

Why do we use "thin" hose for our air,? Cost, ? handling difficulties in and out of water. ? Why walk on thin ice ?
Why not combine two hose sizes if operating long lines, or deep water, or two divers ?
Try: 40 metres of 16 mm, reducing down to 8 or 10 mm for additional length or doubles.

Any increase in flow volume/rate suffers a lot more pressure flow drag loss as it travels down an air pipe. This "delay" in the capacity for the air to "flow" can in itself create a "temporary" negative pressure differential at the "moment" you inhale.

This "delay" causes further breathing demands, and as your breathing effort increases, that "temporary" negative pressure becomes more severe and/or permanent. !!!... It occurs if the air line is too small in diameter to accommodate user demands....

The greater the pressure differential between the outside water pressure and compressor air "in line," the less chance for negative pressure drop to occur on inhaling. The IA receiver "compensates" for "any" temporary partial pressure drop on "inhale" due to either low partial pressure in line, or slow air flow in pipe due to sudden great air demands by one or more "on line."

The IA receiver is not a "substitute" for an "unseaworthy" air supply unit, it is an added safety factor to assist divers in times of physical duress and mental "stress."

Ensure you purchase the correct size air supply unit for your operational needs. Ensure that another's unit offered for your temporary use IS of a capacity to suit YOUR needs.

Be aware that hoses can easily be sucked into turning propellers. If you are concerned that a hose may be cut by the boat propeller if the boat is being manoeuvred during diving, prop guards can be custom built.

If you are concerned, fit a non-return valve in the hose line 10 metres from the boat, thus if the hose is cut, all the air does not rush out, and no instant pressure drop to the diver.

Bigger diameter hoses hold more air reserves. 16 mm holds x 4 more vol than 8 mm. 8 mm x 50 mtr holds 2.5 L. 10 mm x 50 mtr holds 3.9 L. 16 mm x 50 mtr holds 10 Litres, x 8 Bar = 80 L reserve, = 20 breaths at 90' depth. "Talk" is cheap, try a 10 mm hose if on an 8 mm.

~ Lung particle absorption ~

Our lungs have an enormous "sponge volume." We can operate on as little as 15% of their total capacity before we become aware of a "clogging" problem (unless you are a runner). They can "absorb" a lot of unseen contaminants over the years from many sources before we notice it, but when we do notice the effects of it, the process is usually irreversible.

Oil is "expressed" out of a compressor in three ways, as "liquid," as "fine aerosol spray," and as "vapour," The first two are easily extracted by the "coalescing" of the water & oil that join together. Some vapour is also thus extracted as above if the system is "cool."

The hotter the air, the easier it is for the oil to vaporise, and for the dangerous vapour to travel through to the diver. So the more efficient the "after-cooler" is, as in: "air coil cooled by compressor fan & water coil," the cooler the air is, and the vapours coalesce more easily with the water condensate, and are "collected" by filter 1. And more easily the remaining vapour is filtered out by the rest of the system.

A compressor that is new or in good condition and one running "cool," may use only about 1 ml oil per 100 hours "used," thus oil passing into the system is minimal. A worn unit may "deliver-up" 10 ml or more in this time, and if it is running hot, that becomes a lot of dangerous oil vapour, and Carbon Monoxide may be produced. Do you know how much oil is consumed by your compressor?.

What the dynamic impact filter does, is to separate out as much subsequent vapour as possible before the air flows to the final filter. This "eases" the amount of effort required by the final activated carbon & felt system, thus ensuring at all times that the diver is receiving clean air. Even if a diver is at times lax about changing the activated carbon filter. It is a "safety first" system.

Clean adequate air is a daily must, and a quality filter is of great personal value.

Never assume that another's unit has clean filters in it. It is your responsibility to open and check any unit before diving, even your own if it was last checked the day before. You are personally responsible for your daily actions. Never blame others for any reason.

Always check the positioning of the compressor air intake. It needs be firmly secured and situated in a safe place. IT is the beginning of your "life line." Make sure that all aboard the vessel understand its primary function and "why" it must be well away from carbon monoxide fumes.

Any sign of loss of focus (disorientation, or objects within your vision spinning slowly) when diving, could mean contaminated air, surface immediately and as you so do try to not inhale any more contaminated air on the way up.

Even if you do not yet suffer any respiratory problem, disinfect the air and filter system monthly or so by flooding it with the prescribed or other good disinfectant. The air hoses may also be left flooded for an hour within the solution to ensure they too are kept bacteria free.

The regulator mouthpiece should be daily "dipped" in the solution and left hanging to dry. There is an enormous amount of bacteria in saliva. Always flush out well any part of the system that will remain "wet" after disinfecting. Any disinfectant can irritate mucous membranes.

Purified safe air is the sum total requirement for the survival of your fleshly biological "spacesuit" on this material planet. Other than "air," it does yes need food and water. Its one thing to be a diver once a month for pleasure, but another to be a commercial operator. Good air hygiene !!

~ Acute emotional trauma ~

Be aware, that acute emotional trauma can arise from the emotion of fear. This may lead to a condition called hypo-ventilation that may result in unconsciousness and death. This may happen to divers that find themselves in a situation that 'arouses' a powerful emotion of fear. The paragraphs below are an extract from the 'suicide document' on the web site given, and the full text of pages 21-23 of that document need to be examined and understood by divers.

Shock is caused by the trauma experienced, be it from physical or spiritual conditions. The result of this shock causes an immediate failing of the normal respiratory action of the lung movement, shallow small fast breaths commence that affects the oxygen supply to heart and tissues.

This shallow fast breathing which accompanies shock leads to hypoventilation that reduces oxygen intake. Reduced oxygen intake has the effect of a subsequent reduction of carbon dioxide manufactured and expelled, this leads the body to falsely assume that it has enough oxygen and breathing may stop.

(See 'note' end of page 23 of the suicide doc - < suicide.htm >).

As said, the greatest danger to divers is ones "Mind." Within our physical body, is a spiritual one, and IT dictates the actions of the fleshly body through emotions (feelings positive or negative) that are the "pipe line," the telepathic mental link (spiritual air delivery line) of thoughts, either (positive or negative).

If you find yourself in a difficult situation, an emotion of fear may erupt, IT has the capacity to allow confused thoughts to flash in. These lead to not only panic, but to totally irrational deeds. Any intrusion of negative confusing thoughts needs be instantly corrected.

Stabilising the mind, whether above or below water is most easily accomplished by focusing on a given object. The best known, is to visualise the Bright Morning Star It is a consciously visible sign of Light that can help to calm the rising negative emotion and halt the irrational thought flow.

~ Progress ~

Try and see clearly how man's progress has "evolved" through trial and error over time. All progress stems from the "thoughts" of man, many mistakes occur. If you as most of us, have suffered the consequences of having heeded wrong advice, or denied good advice given in any area, or used obsolete or faulty equipment, remember, the fault is only your own. There is never a time to "point the bone" so to speak. Go your way humbly and wiser.

Try and use only stainless steel air containers and compressor unit frame if it is to be used as an air container. This assists ensuring clean air. It is "irrational" to only observe the "outward" appearance of equipment. Your breath of life depends on what is "hidden" inside. Be it your soul or invisible air. Without exception, I have found that most people just "assume" their air delivery system will be OK. They also "hope" that the filters are adequate.

Do NOT rely solely on what others say or offer - seek the truthful reality for yourself, thus only is your destiny truly in your own hand. Check ANY filter system offered for your use before you dive, be it a friends unit or other commercial facility.

Some companies advertise "Diving compressor." You may "think" it is a better machine than another. What determines a "diving compressor"??. nothing actually. Most are basically just piston driven air pumps, all with cylinders that require lubricating with oil. All can contaminate the air. True, there are some diaphragm types that are oil-free air delivery. You would needs 'source' these yourself.

Just because one may have a different intake fitting for an air hose etc, does not mean it is better than another. For "corrosive" situations, I recommend an aluminium unit, less corrosion, also compressors need a fan on the flywheel to cool cylinder fins.

~ Hot oil - hot fumes ~

"Hot" compressors "deliver" oil fumes, and may cause "partial combustion," this releases carbon monoxide which may become of fatal volume, IF you have a headache after surfacing, your unit IS releasing CO, attend to it immediately.

Spray all mild steel parts on engines or boat fittings with "Techtryl," this inhibits rust for many years. A slow running "big" capacity pump geared to low air volume output runs cooler, lasts longer.

Man has for ages time been "Hell-bent" on manipulating others by control through regulation, This manipulation stems from some "believing" that their "forceful" actions are justified, because "they" know better than you, and: "It is only for your own good." Causing much suffering, ill feeling and financial loss, that now leads to confrontation all over the planet..

Freedom is what life is all about, the freedom to choose. If you decide to choose the foolish or dangerous course and end up "on the rocks," that is your God given choice to so do. Personal responsibility.

Now is truly the time for Education and not Regulation. Education, so that you can be in a better position to make the correct choice. So lets gather up our individual expertise and share it around the planet for the benefit of all. Lets put "all the food" on the plate, this way we will see what has become "stale" and "contaminated."

What are your needs? What do you want changed ?

Divers 4 stage Purified Air Safety System

Timothy's filtration system has been primarily developed with the divers "breath of life" in mind, and incorporates added safety to air supplies. Filtration of compressed air for divers as well as industry has its difficulties. Not only this, but for divers where Pure air is needed, there is usually an expensive on-going cost for the "processing" of the air.

What is offered to the diver that is "different" ? for many filter systems exist.

Basically, a unit of four filters that incorporate: Filter:-

1 -- an efficient centrifugal coalescing water/oil/particle separator.
2 -- a high air speed dynamic impact oil vapour collector/extractor.
3 -- a "self fillable" activated carbon filter that can be "re-charged" for a few dollars on a regular basis. This filter also uses two or three layers of thick 10 mm Laroux treble damper felt for oil and particle containment. This 4" long filter is 2.5" wide and contains some 200 gm activated carbon.

This unit has an "in built" safety aspect, it is loaded from the bottom, with a perforated mesh screen on the outlet, thus ensuring that no amount of air pressure can force the felt out of the top. Being "wide bodied," the airflow past is slow, with ample "time" for air contact with carbon contents.

4 -- a secondary centrifugal separator added as a safety particle collector, this unit will separate and "contain" any carbon particles flowing out of the filter 3 system due to incorrect loading of the felt pads by the operator.

Units 2 & 3 & 4 above use natural air flow dynamics and thus no "insert" replacements with on-going costs are used.

The air flowing through these three separators has a "free flow" at all times, and does not "pass through" contaminated inserts as in other types.

The unit is designed to be mounted "away" from the vibrating compressor motor, easily adapted to any boat, and incorporated into any present air delivery system.

The "base" tube has a "socket" at the end, thus ensuring that you can "link in" to your present air receiver system.

The unit is fabricated in stainless steel. Not only safe against being damaged, but for the commercial diver it can be easily taken home, washed out with detergent & disinfectant internally monthly or so, and thus kept squeaky clean at all times.

The main activated carbon contents replacement cost is only $ 3, recommended change every 100 hours with one diver use up to 20 mtrs. Deeper diving and/or two diver operation, change carbon every 40 hours..  A mechanically sound operating compressor is as important as the filter system.

~ Tim's 4 filter stainless steel safety filter unit for "Hookah" divers. ~
15 cu'/min - 250 psi - approx dimensions - 17" x 17" sq x 3" depth.

This document is educational and you may copy the design and have it manufactured by a manufacturer of your own choice.

A 'life long' investment


DIVER'S 'Safety ALERT' Notice
to Compressed Air Suppliers and "Hookah" users.

For many years there has been a continuation of "bad habits" throughout the diving fraternity, as well as some diving compressor unit manufacturers by wrongly recommending the use of either vegetable oils or medicinal oils for use in air compression pumps.

This practice continues on today, in spite of many persons suffering either headaches, bronchial problems and/or death from Carbon Monoxide (CO) poisoning. Part of this "continuance" is because "new" operators ask "old" operators, and habits are hard to change.

Here is some information to you personally, be you an aqualung diver who "assumes" the air dive shop knows what it is doing, and for the dive shop operator, the "Hookah" user, or oil supplier.

Friction causes heat.
Air compression also causes heat.
Heat is what causes oil to vaporise and flow through the system.
Heat causes moisture in the air to "contaminate" the oil and causes it to oxidise and become unstable as a lubricant.

Heat also causes the partial "burn" of oil vapour that results in Carbon Monoxide forming, thus contaminating the air.
Vegetable oils oxidise readily at 70 degrees C, and thus become quickly choked with deposits, and are poor lubricators and dangerous to users.

All refined medicinal oils such as Shell "Ondina 68" and BP "WM 1- 6" that have been "assumed" to be not harmful to humans are as "toxic" as any oil if they overheat. Not only this, but all oils release vapour at certain temperatures. Prolonged inhalation causes pulmonary oedema and consequent lipoid pneumonia. All oil mist interferes with the breathing process.

The refined medicinal oils listed above as well as many unlisted are refined to the point that they contain no antioxidants. Thus, oxidisation occurs easily with the resultant change in composition of the oil structure, heavy black deposits may form in the oil, and lubricating qualities drop, excess heat forms and partial vapour burn occurs, with the resulting insidious CO contamination of the air supply.

Any CO poisoning remains unnoticed when at an increased pressure depth. However it has a 300% more affinity to the haemoglobin than oxygen, and it rapidly displaces the oxygen from the haemoglobin. In the event that there is even as little as 5% CO contamination of the haemoglobin, there is an impairment to mental faculties, and on surfacing, the diver will get a headache.

In the event that this percentage rises to 40%, it will still remain unnoticed at depth, but on surfacing, the diver would suffer a collapse and instant death. Any form of visual impairment or nausea/headache on surfacing must be attributed to air contamination and the mechanical problem rectified immediately.

Nitrogen Dioxide is also produced by partial combustion, it has a distinctive odour, it causes emphysema, bronchitis and is an eye, nose and respiratory passage irritant.

Air compressors MUST only use the correct "dedicated" lubrication that contains the necessary additives and antioxidants, and needs to be fan cooled or water cooled, and run on a 60/40 basis to ensure that cylinder head temperatures remain low, and thus there is NO partial combustion taking place.

"After-coolers" have absolutely no effect on CO already formed in the cylinders, they are merely to assist in reducing the volume of water condensate drawn out of the air stream.

NOTE: CO (Carbon monoxide) is not removed by carbon filtration.

IF you are using a piston compressor, use Shell 'Corena P 100,' or BP 'RCR 100.'  If using a rotary compressor, use BP 'RCS 100' or Shell 'Mandrela 68,' OR the appropriate oil from another oil company.

From tests run with a 5.5 hp motor with a 22 cu'/min swept vol compressor using the correct dedicated compressor oil, the engine ran at 2740 rpm. Changing to the non dedicated oil "Ondina 68," the revs dropped to 2650, a drop of 90 rpm, clearly showing a loss of rpm due to poor lubrication.
Poor lubrication results in heat, more so as the oil viscosity slowly deteriorates due to oxidisation.

How is your chest and head ???
Check your oil and compressor cooling today.!!

"Happy Diving"


Go to - Notes on safe anchoring - 26 p.
Anchor 'holding' capacity - the 'catenary' curve - lift & drag considerations - setting the anchor
 multiple anchors - the anchor type - chain & rope considerations - rope strengths - notes
Parachute anchors - Cyclones


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