The purpose of this guiding principle is to present the requirements for gas testing and define the key methods and hazards of testing procedures. This procedure does not intend to duplicate methodology taught during the Gas Tester course. Only workers who have been trained and certified competent to perform gas tests are authorized to proceed with a test. The procedure/methods that are required to carry out the tests shall be as defined by the course.


This guiding principle covers:

  • The hazards which are identified through gas testing
  • The requirements for gas testing
  • Typical gas testing instruments and pre-user checks


Generally, the potential hazards identified by gas testing include: oxygen enriched atmospheres, oxygen depleted atmospheres, flammable/explosive atmospheres and toxic atmospheres.


  • A gas test must be carried out before entering a confined space and should be continued at the frequency stated by the work permit.
  • Gas testing may only be carried out by an authorized gas tester (AGT).
  • Only use certified and calibrated instruments to carry out gas testing.
  • Work may only be started after clearance has been given by the AGT.
  • If conditions deteriorate, work must be immediately stopped and corrective measures must be taken before work can be re-started.

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Guiding principle gas testing introduction

Gas testing