California ICC UST Inspector Practice Exam

Which condition regarding hazardous atmospheres is NOT true?

1. Oxygen concentration below 19.5%

2. Flammable vapor above lower flammable limit

3. Carbon dioxide concentration above 1.5%

4. Oxygen concentration above 23.5%

The correct answer is: Carbon dioxide concentration above 1.5%

In evaluating conditions related to hazardous atmospheres, it is essential to understand the implications of different atmospheric compositions. The statement regarding carbon dioxide concentration above 1.5% is not typically recognized as a hazardous condition in the same manner as the other options. Oxygen concentration is critical for human safety; a level below 19.5% denotes an oxygen-deficient atmosphere, which can cause asphyxiation or unconsciousness. Levels above 23.5% signify an oxygen-rich environment, often leading to heightened fire and explosion risks. Similarly, the presence of flammable vapors exceeding the lower flammable limit (LFL) is a well-known condition that indicates a potential for combustion. While heightened carbon dioxide levels can be concerning, they do not pose an immediate explosive hazard in the same way as the other conditions presented. Therefore, the assertion about carbon dioxide concentration isn’t fundamentally associated with a hazardous atmosphere in the context established by the other choices.