Air contaminants detection


On an occasional basis, we have to deplore the loss of human lifes or respiratory problems due to air contamination contained in compressed air cylinder. These incidents are sad and useless. There are several factors leading to contamination: carbon monoxyde, carbon dioxyde and petroleum residues and the presence of other contaminants (dust, pollen, etc).

The presence of all these pollutants in a tank is generally due to poor technical maintenance and low consciousness of the technicians. That’s why, it is normal to ask the last compressor date of inspection as well as the date of the last filter replacement. In any doubt, you can refuse to fill you air tank or use you them. Some forms of contanimation can be detected by a powerfull instrument: your nose.

Grossly, if the air is contaminated, there is a strong probability that it might smell bad. In other situations, it may not smell bad but leave a bad taste like hydrocarbons (oil), rubber, or a bad taste. In that case, it is mostly preferrable not to start the dive or to end it as quickly as possible. It is important to report the situation to the technician in order for him to take actions quickly. Avoid being too confident about comments made to reassure you...taste cannot be discussed and often the technician cannot detect after being exposed to high concentration of pollutants.

At the time, we could try to detect by ourselves the level of the air contamination.

Air quality canadian standard

The breathing air contained in a scuba tank should fully respect the canadian standard CSA Standard CAN/CSA-Z275.2 (catalog no.: CAN/CSA-Z180.1-00).

This standard (when respected) is similar to Air Grade E of the US Compressed Air Association.

The standard establish the maximal level in ppm of impurety present in the air: carbon monoxyde 5 ppm, carbon anhydride 500 ppm, methane 25 ppm, nitrogen dioxyde 0.3 ppm, nitric oxyde 2.5 ppm, petroleum hydrocarbons 5 ppm (oils) and particules 1 ppm, without odor and no other contaminants as defined by the American Conference of Government Industrial Hygienists (ACGIH).

See the Canadian Standards Association (click on health and safety) for more details. When the PDF document is displayed, click on Occupationnal Health and Safety and then on Diving and Pressurised Environmnent in order to reach the last version of the standard.

Air quality international standards

On the AFC International website, you will find a sort review of the International Standards. You must notice that Grade E standard is the only one fitted to scuba diving. The canadian standard has also been updated since.

Contamination process

On the Navy Environmental Health Center website, you will find a detailed explanation about air quality regarding scuba diving Breathing Air Quality as well as information regarding the air compressor maintenance and the presence of contaminants (hydrocarbons or oil residus, CO, CO2)

Warning

The listed products are only a subset of all the detectors that can exist on the market. The technical specifications are only there for an indicative purpose and depend on the manufacturer and are subject to modification without warning. At any time you should always refer to the manufacturer website or its representative.

Air filter and humidificator

AQUATEC GUARDIAN air filter

It is a cartridge which connects to the 1st stage on a low pressure outlet with the air regulator hose. A filter has to be inserted into the cartridge. The maximal operational depth is 130’. The filter functions with normal air but is incompatible with Nitrox or any other gas mixes.

The cartridge costs 60$US and the filter 12$US. You can see an illustration on Aquatec Canada or on Aquatec Taiwan (click on Air filter and then the picture).

The advantage of the system is to filtrate the air inspired (hydrocarbones and dusts).

APOLLO BIO-FILTER air filter and humidificator

It is a cartridge which connects to the 1st stage. The cartridge comes in two format of 3/8" and 1/2". A charcoal filter has to be inserted into the cartridge as well a special tube which has to be humidifed with distilled water. The maximal operational depth is 130’. The filter functions with normal air and with Nitrox up to EAN-40 but is incompatible with any other gas mixes. It is also possible to use the charcoal filter without the humidifier part.

The cartridge costs 200$US and the filter 32$US. See Apollo Sports USA for more details.

The advantage of the system is to filtrate (hydrocarbones residus and dusts) and humidify the air inspired (see the website for more explanations).

Carbon monoxyde detection

C-O-Cop

Lawrence Factor sells a carbon monoxyde detector (indicator) C-O-Cop. The detector comes in two versions: the yoke version and the BC version. In both cases, a capsule chemically sensitive to carbon monoxyde (CO) has to be inserted. After the installation of the cartridge on the tank or on the BC, a certain amounts of air has to be released during 3-4 minutes. The color of the capsule change from beige to gray or black according to the level of CO detected. The capsule needs to be replaced after 5-15 tests (according to the air quality tested).

The yoke version costs 75$US; the BC version 49$US. The capsule costs 6$US.

The advantage of the system is to know if the air is contaminated by CO by a relatively quick manner. If the capsule’s color changes, the air is contaminated and should not be used.

CO Experts 2002

Aero MEDIX sells an electronic carbon monoxyde detector CO Expert 2002. It allows to measure concentrations of CO from 5 to 70ppm. It takes a time of about 6 seconds to display the CO level. The detector has been built of residential purposes. A tube connected to a funnel applied toward the sensor in order to avoir false measurements.

The detector costs about 95$US.

The advantage of the system is to know if the air is contaminated by CO relatively quickly. The main desadvantage is that it has not been conceived for scuba diving equipment. And also, the sensitivity of the detector is valid for a year only which the manufacter garanties. It is not recommended for diving.

GasProbe CO

Analox sells a carbon monoxyde detector, the GasProbe CO. The detector can display the CO level from 1 to 1000ppm and cost 299$US. The replacement cartrige cost 99$US and a a lifetime of 3 years.

The advantage of the system is to know if the air is contaminated by CO relatively quickly. The detector needs a startup time of about 10 seconds and can do a reading in few seconds. The detector has not been conceived for diving. External air capture outside the cylinder must be avoided. It needs 9V DC batteries that has to be replaced after ~500hours. The sensor has a lifetime cycle of 3 years.

OxyCheq

OxyCheq sells a carbon monoxyde detection apparitus Expedition CO Analyzer (goto the end of the page). The detector can display the CO level from 1 to 100ppm and cost 329$US.

The advantage of the system is to know if the air is contaminated by CO relatively quickly.

Multi-gas contaminants detection

Analox Sub MKIIP

Analox sells different systems of gas contanimant detection. See the website of Analox (UK) or Amoxtec (US). There is the Analox Sub MKIIP costs about 350$US and allows to measure the carbon dioxyde (CO2) level.

The advantage of the apparitus is its long operational life. Its desadvantage is the fact that it has been conceived to measure the contaminant contained is reduced space (like a dive bell). You need to measure the air exiting form the tank.

Dräger-Tubes & accuro pump

Dräger sells differents detection systems for differents gas contaminants. One of the widely common is the detection gas contaminants using tubes, as the Dräger-Tubes & accuro pump. The system is sold with a detector in which a chemical solution tube is inserted. The chemical solution reacts with the presence of the contaminant. There is a large variety of tubes according to the contaminant level as well as the contaminant to identify.

The system is sold for about 500 to 600$US and each pack of 10 tubes cost on average 80$US or more. In order to have an idea about pricing, consult the catalog of CTS - Air Monitors / Gas Detectors & Chemical Protection Store Catalog (click on Dräger gas detection to obtain the price list).

You also can contact the Dräger company in Montreal: Draeger Canada Limited, 145 Barr, Saint-Laurent, QC H4T1W6, (514)733-3694 (or contact the head office in Ontario 1-905-821-8988).

The advantage of the system is to have a complete picture of the air contamination. Different tubes for each contaminant has to be used for simultaneous detection. At the time of writing, we don’t know if it is possible to take for example an air sample from the BC low pressure air hose exit in some way without damaging the unit (this stills need to be confirmed). The usual procedure is to insert the air sample kit into a large air tight bag, fill the bag with air coming from the tank and then use the pump kit inside the bag to take an air sample as recommended.

Aerotest

Dräger sells another system which connects to a compressed air tank at high or low pressure. The system Aerotest allows you to know in 5 minutes the concentration level of the following contaminants: hydrocarbons (oil), carbon monoxyde (CO), carbon dioxyde (CO2) and water vapor. Exactly what it is needed for scuba diving.

The kits come in different models for high or low pressure with or without tubes. The Aerotest Simultan HP kit (high pressure < 4500psi) costs 2,910$US (complete version with tubes). The Aerotest Simultan LP kit (low pressure < 175 psi) costs around 1,893$US (complete version with tubes). The Aerotest Alpha kit (low pressure < 150 psi) costs 1,245$US (complete version with tubes).

When bought in complete version the Aerotest includes the tubes (4 boxes of 10 tubes: CO, CO2, hydrocarbons, water vapor). The replacement tubes are sold on average 80$US for a pack of 10 (the prices vary according to the contaminant to be tested).

The advantage of the system, despite its high price, is to quickly know if the air is contaminated or not, and consequently allows a more secure dive from the air quality point of view.

Instant Air Check Sampler Kits

Analytical Chemists sells an analysis kit similar to the Aerotest but at a lower price. The kit Air Check Sampler allows you to know in few minutes the concentration level of the following contaminants: hydrocarbons, carbon monoxyde (CO), carbon dioxyde (CO2) and water vapor. Exactly what it is needed for scuba diving.

The kits can work at high or low pressure and come with tubes It costs about 1200$US or less depending on the options.

The advantage of the system, despite its high price, is to quickly know if the air is contaminated or not, and consequently allows a more secure dive from the air quality point of view.

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