An explosimeter reading of 4% or less indicates what entry condition?

An explosimeter reading of 4% or less indicates what entry condition?

• A. You can enter the tank without a respirator for 8 hours
• B. Entry is prohibited
• C. You must wear a respirator at all times
• D. You can enter the tank for brief periods

Answer: (A)

Explosimeter readings tell you how much flammable vapor is in the air, expressed as a percent of the lower explosive limit (LEL). The LEL is the minimum concentration of fuel in air that can ignite. When the reading is 4% or less, the mixture is too lean to sustain an explosion, so entry is permitted without a respirator for up to eight hours, assuming ventilation is adequate and there are no other hazards present. This indicates the atmosphere is not within the flammable range, making it safe to work without respiratory protection for that period. If the reading climbs above 4%, the atmosphere becomes more flammable, and you’d need to adjust the entry plan accordingly, typically increasing protection and monitoring.

Explosimeter readings tell you how much flammable vapor is in the air, expressed as a percent of the lower explosive limit (LEL). The LEL is the minimum concentration of fuel in air that can ignite. When the reading is 4% or less, the mixture is too lean to sustain an explosion, so entry is permitted without a respirator for up to eight hours, assuming ventilation is adequate and there are no other hazards present. This indicates the atmosphere is not within the flammable range, making it safe to work without respiratory protection for that period. If the reading climbs above 4%, the atmosphere becomes more flammable, and you’d need to adjust the entry plan accordingly, typically increasing protection and monitoring.