Quick answer
Gas testing (atmospheric monitoring) checks the air inside a confined space before and during entry. It measures oxygen level, flammable gases, and toxic contaminants to confirm the atmosphere is safe. Because conditions change, testing isn’t one-and-done — it’s done before entry and monitored throughout the work.
What gets tested
- Oxygen — too little (asphyxiation risk) or too much (fire risk)
- Flammable gases/vapours — measured against the lower explosive limit
- Toxic gases — such as carbon monoxide or hydrogen sulphide, depending on the space
Before and during entry
Test from outside the space first, at different depths where practical, because gases stratify. Keep monitoring during the work — a space that tested safe can change as work disturbs residues or as ventilation shifts. Calibrated, well-maintained gas detectors are essential.
Who can do gas testing?
Only a trained, competent person should test and interpret results. Two nationally recognised units are relevant: RIIWHS202E Enter and Work in Confined Spaces and, for dedicated testing, MSMWHS217 Gas test atmospheres.
See the Confined Space course → · Gas Test Atmospheres course →
Frequently asked questions
What are the three things gas testing checks?
Oxygen level, flammable gases, and toxic contaminants.
Do you test once or continuously?
Test before entry and monitor continuously during the work, because the atmosphere can change.
What training covers gas testing?
RIIWHS202E (confined spaces) and MSMWHS217 (gas test atmospheres).
Get trained to test and enter safely
FMS Training (RTO 45189) delivers RIIWHS202E Enter and Work in Confined Spaces. Explore the course →
Last updated June 2026 · FMS Training, RTO 45189