For how long can short-term exposure limits be safely repeated during a workday?

Short-term exposure limits (STEL) are crucial for ensuring that workers are not adversely affected by hazardous substances in the workplace over a brief time. These limits are typically measured over a 15-minute period and are designed to prevent acute or immediate health effects from short bursts of exposure.

The correct choice indicates that short-term exposure limits can safely be repeated four times during a workday. This means that workers can experience exposures that meet the STEL criteria up to four separate intervals within a workday, provided that there are sufficient breaks in between those exposures to allow for recovery. The rationale behind this guideline is to allow workers to safely manage the cumulative impact of exposure while minimizing health risks that can arise from repeated short-term contacts.

In practical terms, adhering to this four-time limit helps ensure that the overall exposure remains within safe thresholds, preventing potential toxic effects that could occur if a worker were to experience STEL violations repeatedly without adequate rest between exposure periods. This regulated approach underscores the importance of both exposure duration and frequency in occupational health practices.