Refrigerated spacesEnclosed spaces that are maintained at low temperatures by an ammonia refrigeration system such as refrigerated rooms and cold storage areas, must have doors that can be opened from inside the space. They must be fitted with an alarm that can be activated from inside the refrigerated space by someone trapped in the space. If there are no personnel present to respond to an alarm, a second door or knockout panel that can be readily opened from the enclosed space must be installed (CSA B52 section 9.2.)