Given that there are several hundred limits it would be a nonsense trying to memorise them. Although as an A4 publication the HSE’s list of Workplace Exposure limits, EH40, is too big to fit in your pocket (the TLV list is much handier and pocket sized), it’s easy enough to keep in your briefcase or kit bag. Even if you leave it in the office, it generally wouldn’t take too long to find the limit you need in most cases.
These days it’s even easier to check the list as EH40 is now published online by the HSE and can be downloaded as a pdf file here free of charge. I keep copies on my laptop and on my phone so I can consult it whenever I need to.
Of course, most hygienists over the course of time will tend to memorise some limits – for substances they come across regularly. Even then it can be dangerous to rely on memory. Limits can change and you can find yourself quoting an out-dated limit if you’re not careful. Which could lead to misinterpretation of sampling results and inappropriate advice on controls if you don’t double check the limits first.
*TLVs® – the Threshold Limit Values published by the American Conference of Governmental Industrial Hygienists