142.TLV

The Threshold Limit Value on ships represents the concentration of manoeuvrable substances and exemplifies the conditions under which the workers should be allowed to be repeatedly exposed for a working lifetime without inauspicious health impacts.

The value is basically estimated depending on the known toxicity level found in humans of a particular chemical matter. This also relies on the accuracy of the sampling and analytical methods, which is not definite as there are other modern means to modify the risk assessment of substances and improve analytical detection limits.

Types of Threshold Limit Value

There are mainly three types of TLV, which are:

1. Threshold limit value – Time weighted average (TLV-TWA): approximated with the average of indefinitely continued exposure on the basis of eight hours a day, five day a week schedule.
2. Threshold limit value – Short-term exposure limit (TLV-STEL): estimated with regards to the assessments by spot exposure for an exact duration of 15 minutes which can be repeated for a maximum of 4 times per day with at least a break of 60 minutes between two exposure periods.
3. Threshold limit value – Ceiling limit (TLV-C): this calculates the absolute exposure limit by converting the Time weighted average into a certain value that should not be exceeded at any time.