{"id":42231,"date":"2026-06-22T20:15:12","date_gmt":"2026-06-22T07:15:12","guid":{"rendered":"https:\/\/www.drivingtests.co.nz\/resources\/?p=42231"},"modified":"2026-05-19T20:22:12","modified_gmt":"2026-05-19T07:22:12","slug":"atmospheric-testing-for-permit-issuers-as-part-of-the-permit-to-work-system","status":"publish","type":"post","link":"https:\/\/www.drivingtests.co.nz\/resources\/atmospheric-testing-for-permit-issuers-as-part-of-the-permit-to-work-system\/","title":{"rendered":"Atmospheric testing for Permit Issuers as part of the permit to work system"},"content":{"rendered":"\n

Some work environments have atmospheres that can injure or kill. Confined spaces, tanks, vessels, pipelines, excavations, and areas near chemical processes can all contain air that is unsafe to breathe or that could ignite. You cannot detect most atmospheric hazards by smell, sight, or feel. By the time a person realises the air is wrong, they may already be incapacitated. Atmospheric testing is the only reliable way to confirm whether a work area is safe for people to enter, and we cover this in our permit issuer training course<\/a>.<\/p>\n\n\n\n

As a Permit Issuer, you need to understand when atmospheric testing is required, what is being tested for, how to interpret the results, and what to do when results fall outside acceptable limits. You do not have to carry out the testing yourself, but you review and approve the results before authorising entry. If the results are not recorded on the permit, or if the testing has not been done to the required standard, you do not issue.<\/p>\n\n\n\n

When testing is required<\/h2>\n\n\n\n
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Atmospheric testing is required whenever the work involves entry into a confined space or any enclosed area where the atmosphere could be contaminated. It is also required when work takes place in or near areas that may contain flammable vapours, toxic gases, or oxygen-deficient or oxygen-enriched air. Hot work in or near hazardous zones requires atmospheric testing to confirm the area is free of flammable vapours before any ignition source is introduced.<\/p>\n\n\n\n

Your organisation’s procedures will define the specific situations that trigger testing, but the general rule is straightforward: if there is any possibility that the atmosphere is not normal air, test it before anyone enters.<\/p>\n\n\n\n

What is being tested for<\/h2>\n\n\n\n

There are five categories of atmospheric hazard.<\/p>\n\n\n\n

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Oxygen level is tested first because it affects both human survival and the reliability of other test readings. Normal air contains approximately 20.9 percent oxygen by volume. The safe range for entry is generally 19.5 to 23.5 percent. Below 19.5 percent, a person risks impaired judgment, loss of consciousness, and death. Above 23.5 percent, materials that would not normally ignite can catch fire, and clothing and hair become dangerously flammable.<\/p>\n\n\n\n

Combustible or flammable gases and vapours are measured as a percentage of the Lower Explosive Limit (LEL). The LEL is the minimum concentration of a gas or vapour in air that will support combustion. Testing equipment reads this as a percentage: 0 percent LEL means no detectable flammable gas; 100 percent LEL means the atmosphere has reached the point where ignition is possible. For general entry, most organisations set the limit at below 5 percent of the LEL. For hot work or any activity involving an ignition source, the limit is 0 percent. There are no exceptions to the hot work limit.<\/p>\n\n\n\n

Toxic gases such as hydrogen sulphide, carbon monoxide, ammonia, chlorine, and sulphur dioxide are measured against Workplace Exposure Standards (WES) set by WorkSafe New Zealand. The permit limit for entry is typically below 50 percent of the WES, or below the organisation’s own standard if that is tighter. Different gases have different toxicity profiles. Hydrogen sulphide, for instance, deadens the sense of smell at higher concentrations, which is why relying on the characteristic rotten-egg smell is unreliable and dangerous.<\/p>\n\n\n\n

Metal vapours are generated by welding, cutting, grinding, and other hot work on metals. Prolonged exposure can cause metal fume fever, respiratory damage, and long-term health effects. Testing for metal vapours is particularly important when hot work is being carried out in enclosed or poorly ventilated spaces.<\/p>\n\n\n\n

Combustible dusts in suspension can explode when exposed to an ignition source. Grain dust, flour, coal dust, wood dust, and some metal powders are all capable of producing a dust explosion. Where the work area may contain combustible dust, testing and dust management controls must be in place before work begins.<\/p>\n\n\n\n

How testing is done<\/h2>\n\n\n\n

Atmospheric testing must be carried out by a competent person using calibrated equipment. Calibration must be current and traceable to the manufacturer’s specifications and the organisation’s procedures. A gas detector that has not been bump-tested or calibrated is not a reliable instrument, and results from it should not be accepted.<\/p>\n\n\n\n

When testing a confined space or enclosed area, test at multiple heights. Gases behave differently depending on their density. Heavier-than-air gases settle to the lowest point. A sewer pit may have safe readings at the manhole opening but lethal concentrations of hydrogen sulphide at the bottom. Lighter-than-air gases such as methane rise to the highest point. Testing only at the entry point will not tell you what conditions are like elsewhere in the space. Test at the top, middle, and bottom as a minimum.<\/p>\n\n\n\n

Testing must be done before entry and at regular intervals throughout the work. Conditions can change. A space that tested safe at 7 a.m. may not remain safe by mid-morning if the work itself introduces contaminants, if nearby process conditions change, or if mechanical ventilation fails. Results should be recorded on the permit or gas test certificate at intervals defined by your organisation’s procedures. Thirty-minute intervals are common, though some situations require continuous monitoring.<\/p>\n\n\n\n

When results are outside safe limits<\/h2>\n\n\n\n

If the atmosphere cannot be brought within safe limits through ventilation, entry may still be possible using respiratory protective equipment such as self-contained breathing apparatus (SCBA). But this changes the permit requirements significantly. The risk assessment must account for the additional hazards of working in a contaminated atmosphere, the rescue plan must be updated to reflect the conditions, and the people entering must be trained and competent in the use of the equipment. Working in breathing apparatus is physically demanding and limits communication, visibility, and duration of the task.<\/p>\n\n\n\n

If the atmosphere is flammable above 5 percent LEL and cannot be ventilated to safe levels, entry should not proceed. If the atmosphere is above 0 percent LEL and hot work is planned, the hot work does not proceed under any circumstances.<\/p>\n\n\n\n

Your role<\/h2>\n\n\n\n

You review and approve the atmospheric test results before you authorise entry. Check that the testing was done by a competent person, that the equipment was calibrated, that the readings are within acceptable limits, and that the results are recorded on the permit. If continuous monitoring is required, confirm that the monitoring equipment is in place and functioning before you sign.<\/p>\n\n\n\n

You cannot see, smell, or taste most atmospheric hazards. You rely on the instruments, on the competence of the person using them, and on your own judgment in interpreting what they tell you. If anything about the results is unclear, do not issue until it is resolved.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some work environments have atmospheres that can injure or kill. Confined spaces, tanks, vessels, pipelines, excavations, and areas near chemical processes can all contain air that is unsafe to breathe or that could ignite. You cannot detect most atmospheric hazards…<\/span><\/p>\n

Read more ›<\/a><\/div>\n

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