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June 10, 2014

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Air quality in the workplace: key considerations

 

By Phil Chambers BSc, CMIOSH  Strategic Safety Systems Ltd.

Air quality in the workplace is a reasonable concern; one of the easiest routes for chemicals to get into the body is via the lungs. There are also concerns about air freshness and dust. There are certain considerations that you need to take into account for all of these factors, and several ways in which you can measure their presence in the air:

Temperature, humidity and air freshness.

This is an obvious concern, particularly as we approach summer when we get our sporadic hot days.  There is a minimum temperature of 16°C for most operations but no maximum temperature.  So we must take steps that are reasonably practical should it get hot; in most industrial cases air conditioning is not reasonably practical.  Good air movement is essential, but on hot days, this may not help much.

Fumes

The starting point when considering fumes is that of their source. If we know what may be in the fumes, then we can assess how much of a hazard it may be and then measure its concentration.

Fumes can generally be split into three types: Products of combustion, reaction products and general evaporation.

Products of combustion

In many cases, you should be concerned if such fumes are likely to be present.  If there are vents from heaters or stacks, then these must be sited so that the fumes do not re-enter the workplace.  Similarly, diesel vehicle fumes must be avoided internally.

Reaction products

These, of course, depend on the processes you have in your workplace. Some may be due to chemical reactions and some may be due to hot or similar processes. In the latter case, you may have fumes from soldering operations or isocyanides from glues or paints.  Both of these are hazardous to health.  However, some fumes such as those from hot melt glues may not be hazardous to health, but are unpleasant.  It is best to exhaust these, but if they are not hazardous, then a rigorous exhaust testing regime is not necessary. With specific fumes that arise from chemical reactions, then the risks from these can be assessed and, if necessary, their concentrations measured.

Evaporation fumes

People often correlate smell with risk. This is a mistake, because the human nose can detect some smells where the concentration is only a few parts per million (ppm), whilst the workplace exposure limit (WEL) may be several hundred ppm.  On the other hand, some hazardous substances may have no smell at all.

Just how you assess the risk posed by these fumes depends on their nature. If they are high risk “purple” or “red” substances, you can reasonably expect them to be present, then you must measure them.  If they are “amber” substances, then you could assess them using published data from similar operations in the same industry.

Dust

Again, the risk depends upon the source of the dust.  For benign dusts such as those of paper, then the WEL is quite high.  For others, such as those products containing cobalt, then the WEL is low.  With benign dusts, then the comparison with dust measurements from similar operations may be sufficient.  With hazardous dusts, then quantitative measurement is necessary

Measurement

While you can buy meters with a direct display from some chemicals, there are two common methods for other specific fumes.  The colour-change method has the advantages of being cheap and giving an instant output.  With this method, a specific volume of air is drawn through a glass tube which has a powder calibrated for the substance you are measuring.  The stronger the concentration, the higher up the graduated tube the colour change is.  The prime disadvantages are that sometimes the colour change is not distinct, and other chemicals may distort the reading.  They are, however, good for indicating that a more precise measurement may be necessary.

The other method is to absorb the fumes onto a substrate, seal the sample and sent it to a laboratory for analysis.  Taking this sample may be by drawing a known volume through a sampling tube or it may be by badges which require no pump.  Note that different substrates may be necessary for different substances and you can’t just send it to the lab. and ask them what is on the substrate; you need to specify what you are looking for.  The obvious disadvantage is that the measurement is not immediate.

The final sampling method is for dust.  Again, there are direct-reading dust meters on the market, but the common method is to use a preweighed filter (from the lab.), draw dust at a specific rate though this filter in a holder for a recorded time and to send it back to the lab. who will tell you the concentration.  Different configurations can cope with inhalable and respirable dusts. Again, with substances such as cobalt, then you can ask the lab. for a concentration.  Note that you need a battery-powered pump for this.

I should stress that, if in any doubt, you should use a person or organisation that specialises and has been trained in this subject.  Should you wish to become trained in this topic, then IOSH provide excellent courses which, from personal experience, I recommend.

References:

1. White paper 30 Workplace Atmosphere Measurements downloadable from http://www.strategicsafety.co.uk/Publications.html

 

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