Indoor Air Quality Testing in Air-conditioned Environments

Increasingly people work in artificial environments, not natural environments.  They are very dependent upon ventilation,  air delivery systems, to deliver fresh filtered and conditioned air.   In offices and commercial properties often people complain about discomfort which they attribute to air-conditioning. It may be a lack of fresh air, or contamination of the air by micro-organisms which is the problem. Some people can become allergic to their indoor work environment where they are exposed to fine particles containing mould or yeast fragments. Indoor air quality testing can generally identify the cause of illness and discomfort in artificial environments.

Sometimes perceived problems have nothing to do with the air-conditioning.   It may be poor quality lighting causing eyestrain and headaches or over time disorientation.   It may be associated with stressors at work, which are difficult to quantify given they often relate to individual human interactions and power relations.  It is only by a process of eliminating potential physical contributing factors that the psycho-social factors can become clearer.

Increasingly people are becoming ill, or believing they are ill as a result of spending so long in an indoor work environment.   This has been termed Sick Building Syndrome.    Sometimes assessing for different indicators can identify a cause.    Other tests can indicate the thermal comfort within the temperature conditioned environment.

Regular indoor air quality testing, while recommended in Australian and New Zealand Standards on Ventilation, is not mandated by the law, however it is good practice.   Some owners and managers of commercial and business accommodation commission Indoor Air Quality testing, sometimes through the contractors responsible for maintaining the air handling units.    There is an advantage in having this performed by an independent monitoring business because it avoids potential conflicts of interest or appearance of a conflict of interest, where those responsible for maintaining air handling units may be sensitive about any problems identified in such tests and may imply or apply pressure on the organisation performing the testing to achieve successful results.

The following are common tests performed on indoor air environments with benchmarks:

      • carbon dioxide;  (less than 1,000 ppm (ASHRAE) but less than 850 ppm indicates conformance with ANZS 1668 Part 2)
      • carbon monoxide; (less than 8.7 ppm)
      • volatile organic compounds;(less than 0.5 mg/m3)
      • dust levels;   (less than 0.3 mg/m3)
      • temperature;  (between 20 and 25 degrees depending upon the season)
      • humidity; (between 35 and 60 percent)
      • viable bacteria; (less than 1,000 cfu/m3)
      • viable yeast spores; (less than 150 cfu/m3)
      • viable mould spores; (less than 150 cfu/m3)
      • viable actinomycetes  (less than 150 cfu/m3).

Testing of air-handling units can assist in identifying problems of microbial contamination before they become apparent through air quality monitoring.   Surface contamination can be determined by taking swabs from chiller drip trays or chiller coils, heating coils, or other surfaces in the air handling units, and having them cultured in a laboratory.    Benchmarks sometimes applied are 1,000 cfu/10cm2 for bacteria and yeasts and moulds.   These benchmarks indicate whether the air-conditioning plant  areas sampled are “clean” or not and levels in excess of the 1,000 cfu/10cm2 figure do not necessarily mean that the surfaces indicate a direct health problem resulting from exposure to air from that system.    They are indicative of a potential problem which may become evident at some stage in the sampling of airborne microbial contaminants.   A more useful approach where a number of units have been tested is to focus efforts on cleaning up and diagnosing the causes contributing to the bad performance of these air-handling units, and generally moving towards achieving lower test results with future tests.

While monitoring over a number of days would provide a good picture of atmospheric contamination to monitor a number of locations continuously over time would be very costly.    Identifying peak loads on systems and hence situations where things are likely to be worse rather than better, and conducting a number of tests over may different locations within such a high load situation would ensure that if problems with the systems did exist, they would be apparent in testing and if the conditions under high load were still acceptable, then at other times of less load, the conditions should be even better.   Focussing carbon dioxide testing to a day and time when most people are at work would be a good test of whether sufficient fresh air is provided by the ventilation system.

Situations recently confronted have been office buildings where old and expensive to recondition or replace air-conditioning systems were replaced with split systems as a cost cutting exercise.    These delivered heating and cooling to an office, but not fresh air.   Monitored carbon dioxide levels in such situations resulted in levels well in excess of the 1,000 ppm level.

Carbon monoxide levels can be high if there is leakage of air into the building from underground or poorly ventilated car-parks, or processes such as cooking or heating with gas or other flammables with incomplete combustion.    Sometimes in older buildings, fresh air intakes to air-conditioning systems has been located in the basement of the building in an area near underground parking.

While it is possible for anyone to perform IAQ testing with the right equipment it is important that independent testing free of any potential conflict of interest is performed.   EnvirosapHe provides a competent, independent monitoring service.

Note:  Envirosaphe is said as envirosafe.

Posted in Air Conditioning