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How often do I need to conduct toxic substance monitoring for my workplace?

The frequency of monitoring depends on the level of contaminant compared against the Permissible Exposure Limit (PEL) stated in the the WSH (General Provision Regulations) First Schedule.

The recommended frequencies are:

Ratio (in %)
of concentration of contaminants compared to PEL
Frequency of monitoring
< 10% of PEL No monitoring is required.
A re-assessment should be carried out if there is any change in the process.
10% to 50% of PEL At least once a year.
> 50% to 100% of PEL At least once every 6 months.
> 100% of PEL At least once every 3 months, until the exposure is reduced to be below the PEL by appropriate control measures.