What air monitoring needs to be performed prior to entering a confined space?

Air monitoring should be performed prior to entry. At a minimum, oxygen and LEL levels need to be monitored. In addition, if other toxins are suspected, then those levels also need to be monitored (eg. CO, H2S, Cl2). Air within a confined space should be monitored prior to entry in the following order: Oxygen - test for oxygen first in order to be sure you get an accurate LEL reading. Most combustible gas meters are oxygen-dependent and will not provide reliable readings in an oxygen-deficient atmosphere. Oxygen levels should be between 19.5 and 23.5%.

  • LEL - test flammable gas/vapor levels due to the threat of fire and/or explosion, which can be an immediate and life threatening hazard.
  • Toxic air contaminants - test for impurities such as carbon monoxide (CO), hydrogen sulfide (H2S) and/or chlorine (Cl2).

Show All Answers

1. Can I wear a respirator while performing my job?
2. What is a confined space?
3. What air monitoring needs to be performed prior to entering a confined space?
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5. What is the service life for fall protection?
6. What is the difference between lockout and tagout?