- NORMALLY ABBREVIATED AS TLV-TWA
- MAXIMUM CONCENTRATION OF TOXIC GAS THAT A WORKER CAN BE EXPOSED TO DAY AFTER DAY WITHOUT SUFFERING HEALTH PROBLEM
- TLV IS AVERAGE TAKEN OVER 8 HOUR DAY OR A 40 HOUR WEEK
H2S HAS A TLV-TWA OF 10 PPM FOR 8 HOURS EXPOSURE
- RECOMMENDED INDUSTRY PRACTICE IS TO WEAR BA AT 10 PPM AND ABOVE
- BEST SAFE PRACTICE IS TO WORK AT ZERO EXPOSURE TO H2S
TOXIC CONTAMINANTS ARE MEASURED IN
- PARTS PER MILLION (PPM)
- IF A MILLION PARTS OF AIR BY VOLUME CONTAINS ONE PART OF H2S IT IS 1 PPM H2S IN AIR
SHORT TERM EXPOSURE LIMIT OF HYDROGEN SULPHIDE IS 15PPM
- THIS IS HIGHER TLV WHICH DEFINES THE MAXIMUM CONCENTRATION THAT A PERSON MAY BE EXPOSED TO FOR A MAXIMUM OF 15 MINUTES
- THERE SHOULD BE NO MORE THAN FOUR SUCH EXPOSURES PER DAY,WITH AT LEAST 1 HOUR BETWEEN EXPOSURES
MAXIMUM EXPOSURE LIMIT OF H2S IS 20 PPM
- THIS IS THE CONCENTRATION LEVEL BEYOND WHICH WORKERS MUST NEVER BE EXPOSED EVEN FOR AN INSTANT
