If the worker is in an environment where exposure could be significant, they must be monitored periodically. Tiny tubes collect the samples Monitoring can be can be achieved without scientists visiting to take air samples. A small tube of charcoal is attached to the worker's clothes and the charcoal absorbs the vapours. The tube is then taken to the lab where analysts measure the levels of harmful chemicals absorbed by the charcoal. This is done by using a solvent that desorbs the chemicals and so separates them from the graphite.
Gas chromatography is a key technique used to separate and detect the trapped air components.
This method is used world wide as a standard method for measuring workplace vapours. However, in the past, various quality checks showed that when measuring levels of benzene and other compounds, results varied tremendously from laboratory to laboratory and country to country. This is unacceptable because it is difficult to know which measurement is the correct one and this means the test results cannot be trusted. Conversely, if the result shows levels above the true levels, companies may be wrongly accused of breaking the law. Either way, the cost is great.