Fire Academy Hazmat Practice Exam

STEL stands for Short-Term Exposure Limit and defines the highest concentration of a hazardous substance that a worker can be exposed to for a short period, typically 15 minutes, without experiencing adverse acute effects. This limit is meant to cover brief exposure spikes, not the long-term average over a full shift. It differs from a time-weighted average over 8 hours, which describes a long-term exposure limit. It’s not about a choking hazard threshold. So the correct concept is the maximum concentration allowed for a 15-minute exposure period.