Warm and Cold Environmental Rooms Safe Use

Both warm and cold rooms at MIT use a refrigerant gas (Freon-22, R-12, or MP39) to control temperatures within the room. The gas circulates from the compressor, which is located in a different section of the building, to piping above the ceiling in the warm or cold room. Depending upon the configuration of the equipment, the circulating gas either cools or warms the room. Many rooms are dual purpose and can be converted to either type of room.


The environmental rooms at MIT are inspected every three months by Harris Environmental, one of the largest designers and builders of environmental chambers in the US. The rooms are inspected for piping integrity, refrigerant leaks, and temperature control. Each room is designed according to ASHRAE (American Society of Heating and Refrigeration Engineers) Safety Code for Mechanical Refrigeration 15-1994. The total amount of refrigerant in the systems is restricted so that even if all the refrigerant were discharged into the room, the oxygen level would not fall to dangerous levels. In addition, each room is alarmed so that an alarm goes off if the temperature changes by more than one degree. Most times an alarm indicates that the door has been left open and the temperature has changed. In rare instances, a leak of refrigerant gas has occurred, causing a change in temperature. Generally, the refrigerant level would have to leak by 10-20% before a change in temperature would activate an alarm.


The Freon gasses are considered to have low toxicity. The Threshold Limit Value (TLV) for Freon-22 is 1000 ppm, indicating that daily 8 hour exposure to this level is safe. Nonetheless, at levels above the TLV, freons can cause dizziness and lightheadedness. In 1998, at a neighboring institution, an overnight leak in a Freon-22 containing warm room caused the first employee entering the room to nearly lose consciousness as she worked over culture flasks that were in a shaker on the floor. Freon-22 is heavier than air and the leaking gas had concentrated near the floor.


In the last 15 years at MIT, no incident like the one described above has been reported. MIT has over 100 environmental rooms. This procedure is being written as a reminder to the MIT community about safe work practices in warm and cold rooms. Please observe the following precautions:


  • If an alarm sounds, leave the room immediately. If the door was open, shut it; the room temperature will restabilize and the alarm will automatically reset. If the alarm does not reset and the room is wired into the central Facilities alarm system, a Facilities employee will respond and check the room. In the case where the environmental room is not connected to the central alarm, please call Facilities (FIXIT or 3-4948) and report the alarm condition. Do not enter the room until the Facilities employee has checked the room and determined the cause of the alarm.
  • If you smell any unusual odors, leave the room and call Facilities (3-4948). Freon itself does not have an odor but Freon leaking from pipes will sometimes have an oily odor.
  • If you experience any dizziness or lightheadedness while working in the room, leave immediately, call 100, and report to the Medical Department to be evaluated. They will notify Facilities (3-4948) who will respond and check the air quality in the room.
  • In general, keep the time working in environmental rooms to a minimum. If extended work is necessary, contact the Industrial Hygiene Program (2-3488) for an evaluation of the general air quality of the room during your experimental procedure. Notify a coworker if you are using the room alone for more than a few minutes.
  • In general, work with flammable solvents, corrosive acids, asphyxiants such as nitrogen and carbon dioxide, and open flames (e.g. Bunsen burners) should not be done in environmental rooms. These rooms have either limited mechanical ventilation (20-40 cubic feet per minute) or no mechanical ventilation and rely on opening and closing the door to change the air in the room. Volatile flammable solvents can cause fires or explosions; the exposed motors of the circulation fans are the ignition source. Acids can corrode cooling coils in the refrigeration system causing Freon leaks. Asphyxiant gasses can displace oxygen in the room due to the low ventilation rate. Storage of large quantities of dry ice in freezer rooms can release carbon dioxide and lower oxygen levels. Environmental rooms need to be specially designed in order to conduct chemical work. If you have any questions about chemical work or general air quality in environmental rooms, please contact the Industrial Hygiene Program (617) 452-3477 for an evaluation.
  • Do not have open containers of water in cold rooms: these cause excessive frost in the refrigeration system and lead to malfunction and temperature instability.


The contained atmosphere in environmental rooms and recirculation of most of the air creates a potential for retaining any aerosols that are formed during research procedures. This can lead to cross-contamination of research projects and personnel exposure. Keep these rooms as clean as possible.


If you have any questions about work or general air quality in environmental rooms, please contact the Industrial Hygiene Program (617) 452-3477) for an evaluation.