Breathing Air

COMPONENT	Units	US NAVY Diver’s Air L-1	NFPA 1500 SCBA Charging	CGA Grade D	CGA Grade E	Fed Spec BB-A-1034 II A
Applicable Notes		1 2 6 7 10 12	2 6 8 10	2 6 8 10 12	1 2 6 8 10 12	1 2 3 6 8 9 10 12
Oxygen	%	20 - 22	19.5 - 23.5	19.5 - 23.5	20 –22	20 - 22
Carbon Dioxide	ppmv	1000	1000.	1000.	1000.	500.
Carbon Monoxide	ppmv	20.	10.	10.	10.	10.
Total Volatile Hydrocarbons Including Methane Less Methane	ppmv ppmv	25. -	- -	- -	25. -	25. -
Halogenated Hydrocarbons Including Freons Less Freons	ppmv ppmv	- -	- -	- -	- -	0.2
Oil Mist + Particulate	mg/m³	5.	5.	-	5.	5.
Oil Mist	mg/m³	-	-	5. *	-	-
Particulate	mg/m³	-	-	-	-	-
Particulate Count/Size Range	microns	-	-	-	-	-
Fibers Count/Size Range	microns	-	-	-	-	-
Nitrogen Dioxide (NO₂)	ppmv	-	-	-	-	-
Nitrous Oxide (N₂O)	ppmv	-	-	-	-	-
Sulfur Dioxide	ppmv	-	-	-	-	-
Dew Point per client	ppmv	- 40 ºF	- 65º F	-	-	(- 63º F)
Pronounced Odor	ppmv	None	None	None	None	None
Methyl Alcohol	ppmv	-	-	-	-	-
Benzene	ppmv	-	-	-	-	-
Butyl Alcohol	ppmv	-	-	-	-	-
Isopropyl Alcohol	ppmv	-	-	-	-	-
Methane	ppmv	-	-	-	-	-
Methyl Isobutyl Ketone	ppmv	-	-	-	-	-
Toluene	ppmv	-	-	-	-	-
Vinyl Chloride	ppmv	-	-	-	-	-
Acetylene	ppmv	-	-	-	-	-
Ethylene	ppmv	-	-	-	-	-
Ethane + Other HC	ppmv	-	-	-	-	-

COMPONENT	Units	US Navy Air for Nitrox Prep.	ANDI 2000 Air for Nitrox Prep	AAUS Air for Nitrox Prep	Modified CGA E for Nitrox Prep	US Navy Post Painting of Chambers
Applicable Notes		1 2 6 7 8 9 10 11	1 2 6 8 10 11	1 2 6 8 10 11	1 2 6 8 10 11	7 9 10 12
Oxygen	%	20-22	20-22	N.A.	20-22	-
Carbon Dioxide	ppmv	500	500	500	1000	1000.
Carbon Monoxide	ppmv	2	2	10	10	20.
Total Volatile Hydrocarbons Including Methane Less Methane	ppmv ppmv	25 -	25 -	25 -	15 -	- 25
Halogenated Hydrocarbons Including Freons Less Freons	ppmv ppmv	0.2 -	- -	- -	- -	5 .-
Oil Mist + Particulate	mg/m³	0.1	-	-	-	-
Oil Mist	mg/m³	-	0.1	0.1	0.1	-
Particulate	mg/m³	-	-	-	-	-
Particulate Count/Size Range	microns				Per NASA*
Fibers Count/Size Range	microns				Per NASA*
Nitrogen Dioxide (NO₂)	ppmv	-	-	-	-	-
Nitrous Oxide (N₂O)	ppmv	-	-	-	-	-
Sulfur Dioxide	ppmv	-	-	-	-	-
Dew Point per client	ppmv	-	- 50º F	- 40º F	- 40º F *	-
Pronounced Odor	ppmv	None	None	None	None	None
Methyl Alcohol	ppmv	-	-	-	-	-
Benzene	ppmv	-	-	-	-	1.
Butyl Alcohol	ppmv	-	-	-	-	100.
Isopropyl Alcohol	ppmv	-	-	-	-	50.
Methane	ppmv	-	-	-	-	1000.
Methyl Isobutyl Ketone	ppmv	-	-	-	-	100.
Toluene	ppmv	-	-	-	-	50.
Vinyl Chloride	ppmv	-	-	-	-	2.
Acetylene	ppmv	-	-	-	-	-
Ethylene	ppmv	-	-	-	-	-
Ethane + Other HC	ppmv	-	-	-	-	-

COMPONENT	Units	Pure Oxygen Navy L-2	Pure Medical Air per UPS 27 + NFPA 99c	Pure San Diving Hyperbaric Chambers	PureCSA Canada Z180.1-00	Pure NAVSEA IPI# 0558-839K (MDLs)
Applicable Notes		1 3 6 8 9 10	1 2 3 5 6 10	1 3 6 8 9 10	1 3 6 8 9 10	12
Oxygen	%	> 99.5	19.5 - 23.5	-	20 - 22	0.002
Carbon Dioxide	ppmv	10.	500.	10.	500.	1.
Carbon Monoxide	ppmv	-	10.	-	5.	0.3
Total Volatile Hydrocarbons Including Methane Less Methane	ppmv ppmv	See the compounds below	25 -	See the compounds below	- 5.	0.8
Halogenated Hydrocarbons Including Freons Less Freons	ppmv ppmv	2. 0.2	5. -	2. 0.2	5. -	Long list of Freons and chlorinated hydrocarbons
Oil Mist + Particulate	mg/m³	-	5.	-	1.	-
Oil Mist	mg/m³	-	None	-	-	-
Particulate	mg/m³	-	-	-	-	-
Particulate Count/Size Range	microns	-	-	-	-	-
Fibers Count/Size Range	microns	-	-	-	-	-
Nitrogen Dioxide (NO₂)	ppmv	-	2.5	-	-	0.015
Nitrous Oxide (N₂O)	ppmv	2.	-	2.	.	-
Sulfur Dioxide	ppmv	-	5.	-	-	0.030
Dew Point per client	ppmv	- 81º F	-	- 81º F	- 63º F	-
Pronounced Odor	ppmv	None	None	None	None	-
Methyl Alcohol	ppmv	-	-	-	-	0.2
Benzene	ppmv	-	-	-	-	0.01
Butyl Alcohol	ppmv	-	-	-	-	-
Isopropyl Alcohol	ppmv	-	-	-	-	0.05
Methane	ppmv	50.	-	50.	10.	0.3
Methyl Isobutyl Ketone	ppmv	-	-	-	-	-
Toluene	ppmv	-	-	-	-	0.5
Vinyl Chloride	ppmv	-	-	-	-	-
Acetylene	ppmv	0.1	-	0.1	-	10.
Ethylene	ppmv	0.4	-	0.4	-	10.
Ethane + Other HC	ppmv	6.0	-	6.0	-	0.5

* Although CGA Grade D has a limit for Oil but not for Particulate, the CGA test for oil always reveals the sum of Oil plus Particulate! This is significant because particulate is a very serious contaminant. The NASA Safety Manual lists acceptable levels of solid particles and fibers on surfaced that contact liquid oxygen. We have adopted their criteria for Oxygen Compatible Air.

1. We use Total Volatile Hydrocarbons because the test can only detect volatile or vaporized hydrocarbons (not oil mist). (This is true for all laboratories, not just ours.) The absence of a Total Volatile Hydrocarbon check in CGA Grade D removes an important indicator from the discovery process, therefore we run that test on every sample. (See the section on Our Analytical Methods.)

2. Oxygen content in air from ordinary compressors will always be 20.95% unless it is improperly prepared synthetic air, or compressor air intake located in a compartment deficient in oxygen. For example, oxygen deficiency could occur in a ship's cargo hold or a leak in an air liquification area. Air compressors cannot by themselves increase or decrease the oxygen content of air.

3. Nitric Oxide and Nitrogen Dioxide in compressor air can occur from welding, carbon arc search- lights and, high temperature combustion gases in the immediate vicinity of the compressor intake. The possibility of their presence in compressor air at significant levels is slight except in Fire Dept stations. Sulfur dioxide can only come from combustion of sulfur compounds (such as a gasoline engine or catalytic converter). (In our opinion, inclusion of these 3 contaminants in this specification would only be reasonable if your compressor is located near a steel foundry, oil refinery, or a large combustion source, and you operated your compressor without any molecular sieve filters.) Note the most recent (1985) version of Federal Specification BB-A-1034 no longer requires a check for these compounds, however /P9290 F3 does.

4. CGA Grade J has been erroneously used by some labs as the specification for air used to prepare Nitrox. The CGA adopted this specification only for instrument air - not compressor air. By the way, the term "Modified CGA Grade J air" is a misnomer, there is no such thing as "modified CGA Grade J".

5. Nitrous oxide (laughing gas) is not part of the Medical Air specification, but it is a common hospital anesthetic, and could accumulate near a compressor intake. We have checked one hospital where this actually occurred. We believe that it should always be included in a program that checks medical air.

6. Odor is a very important test which is essentially the first line of defense for a diver. The fact that the observation is subjective does not detract from its importance. Strong odors are an immediate warning of danger and are not acceptable. Compressor air (except Navy air) should be odorless. If your compressor air has an odor, do not breathe it.

7. The Dew Point specification for USN Diver’s air is only appropriate when compressor air is run through a dryer system. Limits given are as of September 2000.

8. Dew Point is primarily a cold climate concern (especially in Canada), however, read about tropical air in our section on Moisture in SCUBA & SCBA tanks. The CGA "suggests" -64 ºF as a reasonable dew point as long as the dew point is no warmer than 10 ºF below the coldest anticipated ambient temperature. (This is especially important for air in cylinders at high pressure). Measuring the dew point is very tricky. It is best done on site with a dew point meter or a color indicator tube. Air that is wet will quickly reduce the filter's ability to "clean up" the compressed air.

9. Halogenated Hydrocarbons are organic compounds that contain one or more of the following atoms: Fluorine, Chlorine, Bromine or Iodine. Chlorofluorocarbons (CFCs) contain one or more atoms of Chlorine plus Fluorine. Although the Canadian Specification allows up to 5 ppmv, any individual halogenated compound cannot exceed 1 ppmv.

10. Specification Sources: (a) Post Painting of Recompression Chambers is per NAVSEA PI 00C3-PI-001; (b) Pure Oxygen (Aviator’s Breathing) is per Mil-O-27210 Type 1; (c) US Navy Air specification for Nitrox preparation is per USN Diving Manual, Vol. 2, Chapter 10, Table 10-2; (d) NASA Safety Manual Chapter 5; (e) ANDI (American Nitrox Divers International); (f) IANTD (International Association of Nitrox and Technical Divers; (g) AAUS (American Academy of Underwater Sciences); CSA Canadian Workers Compensation Board of B.C.(private communication from Bob Stewart @ WCB).

11. No industry wide consensus exists for non-military Oxygen Compatible Air (OCA) Specifications. Our version of "Modified CGA Grade E" takes into account all existing specifications for OCA, effective analytical protocols, safety and practical concerns. The "oil mist + particulate" acceptance level of 0.1 mg per cubic meter was chosen to take into consideration the uncertainties in weighing filters that have a minimum of 2 cubic meters passed through them. (See also our section on Bad Science as well as the section on Sampling and Analysis of Oxygen and Other Gases) Considerations of particle size and quantity are based on NASA criteria for Oxygen systems.

12. NAVSEA: Industrial Process Instruction 0558-839k is a listing of Acetone, Acetylene, Acrolein, Benzene, Carbon Monoxide, Carbon Dioxide, Ethane, Ethanol, Ethylene, Freons (11,12,113 and 114), Formaldehyde, Hydrogen Sulfide, Isopropanol, Methane, Methanol, Methyl Chloroform, Nitrogen Dioxide, Sulfur Dioxide, Toluene, Trichloroethylene, Vinylidene Chloride, and Total Volatile Hydrocarbons. In addition, a general survey for non-target compounds is required. The table shows some of the detection limits, most of which are in the parts per billion range. In situations where ppb detection limits are required, a larger sample is necessary. For example, we typically receive a 1.5 liter steel cylinder pressurized to 90 psi. This specification is being replaced by ..../P9290 Tables F3 and F4.

Breathing Air Specifications - the Most Common (update 9/2004)

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