1-Chloro-1,1,2,2-tetrafluoroethane (HCFC-124a)

Leaks/releases from older refrigeration and air-conditioning equipment, foam production, and aerosol uses; emissions during servicing and disposal [1].

Breathing vapors near leaking equipment or in confined, poorly ventilated spaces; skin/eye contact with the very cold liquid [3][4].

Short-term high levels can cause dizziness, headache, and poor coordination; very high concentrations can displace oxygen and lead to fainting or suffocation. Liquid contact can cause frostbite; in fires it can break down into irritating, toxic gases (e.g., hydrogen fluoride) [3][4]. It is an ozone‑depleting substance and a greenhouse gas; production is being phased out under the Clean Air Act and Montreal Protocol [1][2].

HVAC/refrigeration technicians, foam and aerosol workers, and people near leaking or improperly serviced equipment in small rooms [1][3].

Use certified technicians for service and refrigerant recovery; ensure good ventilation; avoid enclosed spaces with suspected leaks; follow label/SDS guidance; replace with non‑ozone‑depleting alternatives when possible [1][2][3].