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Sealed System
HFC 134a COMPARISON WITH CFC 12
HFC 134a (1,1,1,2-tetrafluoroethane) is being studied as part of the PAFT I programme sector, which began in
December 1987. It is a prime candidate for the replacement of CFC 12 (dichlorodifluoromethane) in refrigeration and
air conditioning systems, medical aerosols, and in certain foam blowing applications. HFC 134a is similar to CFC 12
in that it has a low chemical reactivity and a high degree of stability. Both chemicals are gases.
Inhalation Toxicity
(Short-term exposures to high concentrations, such as accidental leakages)
Both HFC 134a and CFC 12, are very low in toxicity by the inhalation route. The 4-hour LC
for HFC 134a is great-
50
er than 500,000 ppm, and for CFC 12 it is 760,000 ppm. As with other halogenated hydrocarbons, CFC 12 and HFC
134a can, at high dose levels, sensitize the heart to adrenaline. For CFC 12, the threshold level for cardiac
sensitization is 50,000 ppm, while for HFC 134a it is 75,000 ppm.
HFC-134a poses no acute or chronic hazard when it is handled in accordance with DuPont recommendations and
when exposures are maintained at or below the DuPont Acceptable Exposure Limit (AEL) of 1,000 ppm (8 and 12
hour Time-Weighted Average or TWA).
An AEL is an airborne exposure limit established by DuPont scientists that specifies time-weighted average (TWA)
airborne concentrations to which nearly all workers may be repeatedly exposed without adverse effects. The AEL for
HFC-134a has the same value as the Threshold Limit Values (TLVs) established for CFC-12 and HCFC-22. TLVs
are established by the American Conference of Governmental and Industrial Hygienists (ACGIH).
However, inhaling high concentrations of HFC-134a vapor may cause temporary central nervous system depression
with narcosis, lethargy and anesthetic effects. Other effects that may occur include dizziness, a feeling of intoxica-
tion and a loss of coordination. Continued breathing of high concentrations of HFC-134a vapors may produce car-
diac irregularities (cardiac sensitization), unconsciousness, and with gross overexposure, death. Intentional misuse
or deliberate inhalation of HFC-134a may cause death without warning. This practice is extremely dangerous.
If you experience any of the initial symptoms, move to fresh air and seek medical attention.
Cardiac Sensitization
If vapors are inhaled at a concentration of 75,000 ppm, which is well above the AEL, the heart may become
sensitized to adrenaline, leading to cardiac irregularities and, possibly, to cardiac arrest. The likelihood of these
cardiac problems increases if you are under physical or emotional stress.
Medical attention must be given immediately if exposed to high concentrations of HFC-134a. DO NOT treat with
adrenaline (epinephrine) or similar drugs. These drugs may increase the risk of cardiac arrhythmia and cardiac
arrest. If the person is having difficulty breathing, administer oxygen. If breathing has stopped, give artificial
respiration.
Skin and Eye Contact
At room temperature, HFC-134a vapors have little or no effect on the skin or eyes. However, in liquid form,
HFC-134a can freeze skin or eyes on contact, causing frostbite. Following contact, soak the exposed area in
lukewarm water, not cold or hot. If medical treatment cannot begin immediately, apply a light coat of a nonmedicated
ointment, such as petroleum jelly. If the exposed area is in a location where the presence of the ointment would be
awkward, such as on the eye, apply a light bandage. In all cases of frostbite, seek medical attention as soon as
possible. Always wear protective clothing when there is a risk of exposure to liquid HFC-134a. Where splashing is
possible, always wear eye protection and a face shield.
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