Water Vapour Levels in Low-Pressure, Supplied-Air
Breathing Hose
CC Austin
NIOSH-approved breathing air supply hose is used to supply air to firefighters working on aerial ladders and in confined space entry. This low-pressure hose supplies air at a line pressure of 100 psig to the firefighter's Hip-Pac Supplied-Air Respirator regulator, bypassing the 2216 psig emergency escape air cylinder. The regulator then reduces the pressure from 100 psig to the 1 psig required by the positive-pressure face mask. The results of lab analysis of the air entering the face mask indicated the presence of 22 ppm of water vapour. There was no detectable odour when breathing through the face mask supplied with air which had passed through approximately 300 feet of the hose in question. The air-supply hose itself is attached to a 2216 psig cascade and the pressure is reduced to 100 psig before entering the hose by a regulator attached to the cascade. The results of lab analysis of the air entering the hose indicated a water vapour concentration of less than 1 ppm.
Air supplied to firefighters using this breathing-air supply hose meets the requirements set forth in the CAN3-Z180.1-M85 "Compressed Breathing Air and Systems" Standard. That is to say that the air supplied to the face mask at a line pressure of 100 psig must not exceed 45 ppm of water at a 100 psig pressure dew-point of -31 °C. This requirement was met with 22 ppm of water in the air coming out of the 300 foot, 100 psig hose. The air which is supplying the 300 foot hose must not exceed 2.3 ppm of water at a 2216 psig pressure dew-point of -31 °C. This requirement was met with less than 1 ppm of water being found in the air which enters this 300 foot length of hose at 100 psig.