Refrigerants threshold limit value

Toxicity is referenced to the Threshold Limit Value — Time Weighted Average established for each refrigerant. This is defined in ASHRAE Standard 15-1994 as (refer to the manufacturer s product data for more complete detail) ... 

Class A signifies refrigerants for which toxicity has not been identified at concentrations less than or equal to 400 ppm, based on data used to determine Threshold Limit Value-Time Weighted Average (TLV-TWA) or consistent indices from Section 6.1.2. ... 

In a NIOSH Health Hazard Evaluation of refrigeration workers exposed far below the threshold limit values (TLVs) for chloropentafluoroethane and chlorodifluoromethane, 27 workers were medically evaluated. Seventy-one percent complained of dizziness and lightheadedness compared with twenty-one percent of controls. Palpitations were reported in 36% of exposed and none of the non-exposed workers. No clinical neurological or electroneurophysiological abnormalities were detected in eight of the refrigeration repair workers followed for 3 years during continuous employment. ... 

Butadiene is a colorless, odorless, flammable gas, with a bp of -4.7°C. As of 2000 butadiene has been on the Known to Be a Human Carcinogen list of the Department of Health and Human Services. It has a time-weighted average threshold limit value (TLV) of 2 ppm. TLVs and carcinogens will be discussed more fully under benzene. Butadiene is expensive to store because it polymerizes easily and must be refrigerated. 

TLV Threshold limit value (the refrigeration concentration limit in air for a normal 8-hoiu- woriiday it will not cause an adverse effect on most people). 

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