INFORMATION SHEET 4.1-3

INFORMATION SHEET  4.1-3

Threshold Limit Value

 

Learning Objectives: After reading this information sheet, the student/ trainee should be able to;

 

1.   Prevent exposure to substances which could be hazardous to their health.

2.   Distinguish appropriate types of measurement that can affect the health.

     The key to preventing exposure to substances, which could be hazardous to health, depends on the first two steps mentioned – recognition of the hazard or potential hazard, and, evaluation of the extent of the hazard. People in the workplace may encounter hazards from several sources. An important means of evaluation is measurement to determine the extent of the threat.

 

MEASUREMENT – WHICH TECHNIQUE

     The health effects of exposure to toxic substances can be acute or chronic. It will therefore be necessary to distinguish appropriate types of measurement:

1.   Long term measurements which access the average exposures of a person over an extended time period.

2.   Continuous measurements capable of detecting short-term exposures to high concentrations of short-term exposure to high concentrations of contaminants, which cause an acute exposure.

3.   Spot readings can be used to measure acute hazards if the exact point of time of exposure is known and the measurement is taken at that time, chronic hazards may be assessed if a significant number of measurements are made.

SUMMARY OF MANAGEMENT TECHNIQUES
For chronic hazards - continuous personal dose measurements, continuous measurement of average background levels, spot readings of contaminant levels at selected positions and times.
For acute hazards; – continuous personal monitoring with rapid response,  continuous background monitoring with response, spot readings of background contaminant levels as selected positions and times.
For analysis of whether  area is safe to enter: direct reading instruments. Particle qualitative and quantitative analysis can be carried out by direct reading measurements