Indoor air quality: what must be tested, and how often?

Short answer: test when your risk assessment shows that indoor air may fall outside the Table 3 guideline levels, then at the frequency the risk assessment sets or at least every 24 months. The Physical Agents Regulations, 2024 set guideline levels for air temperature, air velocity, relative humidity, carbon dioxide and carbon monoxide. Artificial ventilation systems must also be tested at the manufacturer's intervals, and at least every 24 months.

Indoor air quality falls under regulation 12 and Table 3 of the Physical Agents Regulations, 2024 (Government Notice 5952, Government Gazette 52226, 6 March 2025), which took effect on publication. The ventilation rules in the Environmental Regulations for Workplaces, 1987 fell away when regulation 21 repealed those regulations 18 months after promulgation, on 6 September 2026. The amendment published on 20 February 2026 (Government Notice 7149, Government Gazette 54177) did not change regulation 12 or Table 3.

The Table 3 guideline levels

Table 3 sets these guideline levels:

• Air temperature: 20 to 28 °C dry-bulb.

• Air velocity: 0,1 to 0,5 m/s.

• Relative humidity: 30 to 60 %.

• Carbon dioxide: not to exceed the outdoor concentration by more than 600 ppm.

• Carbon monoxide: 10 ppm.

Two practical points follow. Table 3 states no averaging period for any parameter, so the survey report should explain how readings were taken and compared with the levels. And because the carbon dioxide level is set relative to outdoor air, a survey needs an outdoor reference measurement. Heat stress in hot work areas is dealt with separately, under regulation 10; see our article on heat stress surveys.

Monitoring must also take into account parameters that have no figure in Table 3: other applicable hazardous chemical agents, mould, other applicable hazardous biological agents, and the air requirements for different types of occupancies (regulation 12(4)).

When testing is required, and how often

• Risk assessment (regulation 6): before exposure, as far as reasonably practicable, then at intervals not exceeding 24 months. Review it sooner if, for example, work methods or plant change, controls stop being effective or an incident occurs.

• Monitoring (regulation 7): required where the risk assessment shows that employees may be exposed at or above the Table 3 guideline values, or outside their ranges. It must be done at a frequency determined by the risk assessment, or at least every 24 months. An inspector may direct you in writing to repeat it.

• Ventilation system tests (regulation 12(3)): an artificial ventilation system must be tested by a competent person at the intervals in the original manufacturer's specifications, but not exceeding 24 months. It must be maintained to those specifications or, where there are none, as the risk assessment sets.

• Who: a competent person, using instruments calibrated to a national or international traceable standard. The regulations do not require an approved inspection authority for this work.

• Follow-up: a documented action plan for the report's recommendations, with records kept for 40 years.

Ventilation comes after removing the source

Regulation 12 sets an order. First, eliminate at the source the risk of exposure to hazardous biological, chemical and physical agents that affect indoor air quality, where reasonably practicable. Where that is not reasonably practicable, control indoor air quality to the Table 3 levels with natural ventilation or an artificial ventilation system. An artificial system must comply with the air requirements for different types of occupancies listed in SANS 10400: Part O.

In practice, complaints often trace back to a few causes:

• Too little outside air for the number of people, which shows up as rising carbon dioxide and a stuffy feel.

• Poor air distribution: blocked or badly placed diffusers, draughts, and hot or cold zones.

• Poor maintenance: dirty filters, coils and drain pans in air-conditioning systems.

• Combustion sources: fuel-powered forklifts, generators or gas heaters indoors or near air intakes, which produce carbon monoxide.

• Damp: leaks, condensation and high humidity that let mould grow.

• Chemical sources: cleaning products, printing and renovation work.

A quick self-check

• Check that your physical agent risk assessment covers indoor air quality and is less than 24 months old.

• Find the date of the last ventilation system test and the manufacturer's recommended interval. The maximum is 24 months.

• Confirm that you hold the manufacturer's maintenance specifications. If you don't, the risk assessment must set the maintenance.

• Map complaints about stuffiness, temperature, draughts or odours by area and time of day.

• Look for engines or gas heaters running indoors, and for signs of damp or mould.

How Qualitas can help

Our indoor air quality assessments measure the Table 3 parameters, including an outdoor carbon dioxide reference, and look at ventilation, air distribution and likely sources. The report, written for management, SHEQ teams and auditors, sets out what to fix first.

Our overview of the Physical Agents Regulations, 2024 explains the wider framework. Where a process releases dust or fumes, local extraction at the source usually controls it better than general ventilation; see our article on LEV testing.

Not sure what your site needs? Start with our free Compliance Gap Analysis, request a quote, or call or WhatsApp 082 649 6599.

This article summarises the Physical Agents Regulations, 2024 (Government Notice 5952, Government Gazette 52226, 6 March 2025), as amended by Government Notice 7149 (Government Gazette 54177, 20 February 2026), for general guidance. It is not legal advice; refer to the regulations for the full requirements.

Christo de Wet is a SAIOH-registered occupational hygienist with 15 years' experience and the founder of Qualitas Occupational Consulting.