Picture this: Workers are using a diesel generator in a basement car park or an excavator working inside a building. You can see and smell diesel exhaust fumes in the area, and when you ask what is being done to protect workers from diesel emissions…someone points to the confined space gas detector…and in my head I scream, “nooooooo…”. This happens more often than you think. But why is a confined space gas monitor not enough?
Well confined space gas detectors typically measure oxygen, carbon monoxide, hydrogen sulphide, and the lower explosive limit…all very important, but there are a few other diesel exhaust gases that can cause you problems. The most common ones we see are the oxides of nitrogen such as nitric oxide (NO) or the more toxic nitrogen dioxide (NO2) …and then there is the carcinogenic diesel particulate matter (DPM) that you have to worry about too.
So What Should be Done? The key with all of this is to follow the hierarchy of controls (which is the technical term for not using PPE first).
You want to make sure that you ventilate the area well – which doesn’t just mean putting fans in the building. You need to get rid of the contaminated air, and replace it with clean air. You should consider reducing the amount of time the equipment is idling…so turn it off when not in use – or if it’s a generator – put it outside the car park and run the power leads to where you need them to prevent having an issue in the first place!
You should use a calibrated confined space gas detector (key word: calibrated!!) and a calibrated gas detector to measure oxides of nitrogen in real time. Both of these should be set to raise an audible alarm whenever they reach certain trigger points (I would recommend that being at or below the Workplace Exposure Standard) so that workers leave the area if an alarm is raised.
Monitoring for chemicals in real-time using gas detectors is a common task for any occupational hygienist. There are many advantages to using them, but you have to know how to use them correctly, be sure you are monitoring for the right things, and know their limitations. Sometimes you can use wireless gas detectors if you want to get fancy and your work will occur over a long period of time, or over many locations, which is where these can be helpful…but gas detectors alone aren’t enough.
There are a number of additional things you need to consider to prevent exposure to DPM such as using low emission engines, low emission fuel, proper engine maintenance, filtered operator’s cabins, and PPE…and wherever there is a risk of exposure, you should provide training to your workers in the health effects of the chemicals (eg: the different gases/DPM) that they might be exposed to.
So it’s not really that simple (hence my “noooooo” scream before), which is maybe why it’s still common to see these issues in the construction industry?
Where can I go for help? You should ask your friendly Occupational Hygienist!
(Disclaimer: I haven’t listed all controls to prevent exposure – or even all gases or hazards that come from diesel exhaust…this is just a quick overview….do not rely on this alone….call an Occupational Hygienist!!)