Gases that have density close to that of air should be installed in the breathing zone, aka respiratory zone, which is 4-6 ft from the floor. Gases that are lighter than air should be installed on or near the ceiling, include (but not limited to) ammonia, methane, and hydrogen. Such gases include (but not limited to) carbon dioxide, chlorine, ozone, propane, and refrigerants.

Gases that are heavier than air should be installed 6вЂќ from the floor. The focus, of course, is on what this area contains in terms of toxins and gases and how this area can be accurately tested for safety reasons. This is вЂњ 72вЂќ above the floorвЂќ (ASHRAE StandardвЂ¦). The breathing or respiratory zone is defined as вЂњthe area from which the employee draws air and has been defined as being as close as possible to the nose and mouth and a hemisphere forward of the shoulders with a radius of 6 to 9 inchesвЂќ (Review of ANSI/ASHRAE Standard 62.1-2004вЂ¦).

It states that вЂњdusts, gases, fumes, vapours and mists found in the workplace environment shall be measured in the respiratory zone of workers or, if this proves to be impossible owing to the lack of equipment for taking sampling in this zone, then outside the breathing zone but in a place located as close as possible to such zoneвЂќ (Division V: Air Quality: 44 Methods). Recently, QuebecвЂ™s regulation has reinforced CETCIвЂ™s recommendations. (CETCI) has always recommended that they be installed in the breathing zone.

In contrary, Critical Environment Technologies Canada Inc. In the past, vehicle exhaust gas detectors have been installed on or near the ceiling.

Sampling train breathing zone