el burning appliances that could malfunction and produce this gas. It can also be produced from vehicle engines which should not be run in enclosed spaces with people present. (Solution: Dilution by increased ventilation and investigate source)
Nitrogen oxides NO and N2O are present in air often being produced in conjunction with CO when burning of fossil fuels is taking place. Fertilisers are thought to be another outside source. WHO N2O exposure limits 100ppb over 1 hour and 20 ppb annual limit. Solution: Effective Gas filtration and investigate source)
Sulphur dioxide – Produced from the burning of fossil fuels such as traffic and power stations but also from natural sources like volcanoes. WHO guidelines advise short term (10minutes) exposure of no more than 500µg/m3. Daily exposure less than 125µg/m3. Long term exposure less than 50µg/m3. (Solution: Effective Gas filtration and investigate source)
Ozone – This gas can often be found in outlying city areas and is a very reactive gas that can often be taken up by reaction with Nitrogen oxides. Indoor sources can include office equipment such as photocopiers and UV lights. It is harmful to human respiratory systems and exposure should be limited to levels not exceeding 120µg/m3 over an eight hour period according to WHO guidelines. (Solution: Effective Gas filtration and investigate source)
Formaldehyde –This usually comes from off-gassing of furnishings so is an internal source of pollution. (Solution: Effective Gas filtration and investigate source)
VOC’s – Volatile Organic Compounds are numerous in type and sources. Poorly burned fuels and household chemicals are two sources. (Solution: Effective Gas filtration and investigate source)
Radon – usually depends on the building location as it is a ground source gas that occurs in quite well documented locations around the country. It is a good idea to check the probability of Radon in the location being considered and testing if it is likely to be there. (Solution: Dilution by increased ventilation and investigate source)
All of these contaminants may present a problem. If there is a suspected problem that needs investigating it is worth calling in an expert to make a report and test for the more common problem contaminants we have mentioned and test for any other suspected ones. The HVAC plant itself can be a source of contamination if it is not well maintained. It needs to have the correct design and application of filters to clean the air with regular inspection and cleaning of the duct system on the intake and supply side. The air handling units also need cleaning with attention given especially to the coils and heat exchangers.