Atmospheric Monitoring for Confined Spaces
Construction and general industry · Ver en español
Talking points
- Test the atmosphere before entry in this order: oxygen (19.5–23.5% is safe), then LEL (below 10% for entry), then specific toxics (H₂S, CO, etc.).
- Monitor continuously during the entire entry, not just at the start. Conditions inside a space can change due to work activities, chemical reactions, or weather.
- Calibrate your gas monitor daily per the manufacturer's instructions. Bump-test it with known calibration gas before each use.
- Test at multiple levels — top, middle, and bottom of the space — because gases stratify by weight. Methane rises; H₂S sinks.
- If any reading exceeds the action threshold, evacuate the space immediately, ventilate, and retest before re-entry.
Ask the crew
When was our gas monitor last calibrated, and who is responsible for monitoring the atmosphere during today's entry?
Standards this talk is built on
A toolbox talk is a short safety briefing. It supports the training a standard requires; it does not replace it.
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Sign-in sheet
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