Don't Store Dry Ice in Walk-in
Refrigerators (top)
Walk-in refrigerators (or "cold boxes") typically recirculate the chilled air
in their interiors, so storing volatile materials in them can pose special hazards--any
gases or vapors may concentrate inside over time.
Recently on theX Campus, a walk-in refrigerator was used to store dry ice. The dry ice
was stored in a standard dry ice storage locker, but the locker had been placed in the
cold box to further reduce the rate of dry ice loss. The dry ice, of course, gave off
carbon dioxide (CO2) gas as it sublimed, causing the refrigerator to build up CO2 levels
of 12,000 parts per million (ppm)! In comparison, outdoor air contains only about 400 ppm
CO2, and OSHA's Permissible Exposure Limit for CO2 is 5000 ppm. Although no one was
affected, the incident points out the need to keep volatiles out of walk-in refrigerators.
