What concentration can produce a cardiac sensitization response in the presence of epinephrine?

• A. 50,000 ppm or greater
• B. 1,000 ppm or greater
• C. 5,000 ppm or greater
• D. 200,000 ppm or greater

Answer: (A)

High concentrations of certain refrigerant vapors can make the heart unusually responsive to adrenaline (epinephrine). When exposure reaches about 50,000 ppm or greater (roughly 5% by volume in air), the myocardium can become sensitized, so epinephrine can trigger dangerous arrhythmias more easily than usual. That’s why this threshold is identified as the level at which a cardiac sensitization response can occur in the presence of epinephrine. Lower concentrations aren’t typically associated with this effect, while much higher exposures would also be dangerous, but the statement that captures the known sensitization threshold is 50,000 ppm or greater.