When can a person be exposed to H2S exceeding the LTEL?

• A. A person may be exposed for not more than 15 consecutive minutes if the concentration does not exceed the applicable maximum exposure limit concentration, exposure occurs at not less than 1 hour intervals, not more than 4 times in 8 hours, and the mine has an SOP for working in contaminated air.
• B. A person may be exposed for up to 2 hours without limit.
• C. A person may be exposed only if wearing SCBA.
• D. Never.

Answer: (A)

The key idea is that exposure to H2S that goes beyond the long-term exposure limit is allowed only under tightly controlled, short-term conditions so the average over a shift stays within safe limits. The allowed pattern sets a small, defined time window for a burst of exposure (no more than 15 consecutive minutes) and requires the concentration to stay at or below the maximum exposure limit concentration. It also spaces these bursts with at least an hour between them and restricts how often they can occur within an 8-hour period (no more than four times in 8 hours). Bringing all these pieces together, plus having a documented SOP for working in contaminated air, ensures that even though the LTEL is exceeded momentarily, the overall exposure remains within safe levels over the work shift.

Why this fits best: it provides a concrete, regulatory way to allow brief exceedances without pushing the 8-hour average past the LTEL, using specific duration, concentration, interval, and frequency limits and requiring an approved SOP.

Why the other ideas don’t fit: allowing a 2-hour exposure without limit would push most people past the LTEL over an 8-hour period. Requiring SCBA only when exceeding the LTEL overlooks the structured limits and may be unnecessarily restrictive or impractical in some situations. Never having any exceedance is not correct because there are regulated circumstances where brief exceedances are permitted under control measures.