The answer is.......possibly. Depends on the efficiency of the combustion process eg how well the engine is running as to wether you get carbon monoxide or carbon dioxide. I would suggest that exhaust gases / fumes are treated as a substance hazardous to health and so use COSHH as your guidance - do a simple COSHH assessment. Generally speaking you may not need to measure any levels but would need to use an avoidance and ventilation approach in my opinion.

Hi Jason If you are using diesel engines in a workplace then you should look at and follow HSG187. It has a good indicator of how to assess if you have a problem, in Table 2. I use this as we have gas and diesel counter balance trucks. You could also hire a monitor like an EVM7 which will give you a measure of particles, CO2 and CO. Ian