EH40 - New exposure limits

Published: Friday, August 17, 2018 - 10:44

New exposure limits for 31 substances including Carbon Monoxide and Nitrogen dioxide.

The EU Directive 2017/164/EU introduces the 4th list of Indicative Occupational Exposure Limit Values (IOELV’s) for 31 chemical substances and is designed to protect workers for ill health effects of exposure to hazardous substances in the workplace.  Chemicals currently have two exposure levels for concentrations of a hazardous substance in the air that people breath averaged over a time-weighted average (TWA) there are two periods used long-term exposure known as Workplace Exposure Limits (WEL) with a TWA of 8 hours and Short Term Exposure Limit (STEL) with a TWA of 15 minutes.


The HSE held a consultation which closed on the 2nd of February 2018 looking to implement the minimum requirement to incorporate the new WEL/STEL levels for the 31 chemicals into a revised EH40 document.  In addition, they are looking to take advantage of the 5-year transition for underground tunnelling works and mines for Carbon Monoxide, Nitrogen dioxide and Nitrogen Monoxide.


Examples of the changes.



New levels

(a) WEL

(b) STEL

Existing levels

(a) WEL

(b) STEL

Carbon monoxide



(a) 35mg.m3


Nitrogen dioxide





Nitrogen monoxide





Sulphur dioxide






New exposure limits will impact Ports confined space entry procedures as the monitors being used to test the atmosphere may need to be recalibrated to take account of the new levels.


 In addition as Nitrogen monoxide, Carbon monoxide, Nitrogen dioxide and Sulphur dioxide are all constituents of Diesel Engine Exhaust Emission (DEEE’s) consideration will need to be given to obtaining monitoring equipment for warehouses and vessel operations to monitor potential levels of the above chemicals in the air.  

Special thanks to PSS member Port, Port of Tilbury for sharing this update for the benefit of fellow PSS members. 

facebook twitter share