Non-toxic status is achieved when exposure is maintained below what limit?

• A. 1000 ppm
• B. 500 ppm
• C. 5000 ppm
• D. 100 ppm

Answer: (A)

Exposure limits define when a gas is considered safe enough for routine work. If the concentration stays below that limit, the substance is treated as non-toxic for typical exposure durations, giving a practical safety margin in spaces where vapors can accumulate.

For this item, the standard non-toxic threshold is 1000 ppm. Keeping exposure under 1000 ppm reduces the likelihood of acute toxic effects and keeps safety standing for normal tasks, provided ventilation is adequate and exposure duration is typical. Lower limits, like 100 ppm, would be far more conservative and apply to gases with higher toxicity, while higher limits, such as 5000 ppm, would exceed the usual safety boundary and increase risk before triggering a non-toxic status.