The Risks Associated with HVAC Drip Pans
User Experience Network™ [Health Devices Jan 1996;25(1):43]
Drip pans in our patient room heating, ventilation, and air-conditioning
(HVAC) system sometimes overflow and have been found to contain a variety of
microorganisms. What are the risks associated with cooling system drip pans?
Drip pans catch condensate from cooling coils and either drain the
condensed water to a wastewater line or evaporate the water to the air. These pans are the
same kind that are used in home refrigerators. In hospitals, drip pans are found in most
devices that have a cooling coil, including refrigerators and in-room HVAC units. Most
devices containing drip pans remove condensate by 1) routing it to a drain, 2) allowing
the user to routinely empty and clean the pan, or (3) relying on air moving through the
unit to dispose of the condensate through evaporation.
Various flora and fauna can be deposited and survive in a drip pan. The
likelihood of this occurring depends, among other factors, on the amount of water in the
pan and the quantity of dust, dirt, and soil particles in the air moving through the coils
and over the pan. The fungus Aspergillus and the bacteria Legionella,
commonly found in soil, can be transmitted through the air and have been found in the drip
pans of air-conditioning systems. Mycobacterium tuberculosis, which can survive in
dark, moist areas, may also live in drip pans, although no confirmed instances are known.
Whether such colonization is a concern depends on the configuration of the
unit containing the pan, the location of the pan in the unit, the location of the unit in
the hospital, and the type of organism growths in the pan. Drip pans in some locations may
not circulate organisms to areas where they will contact people. And some organisms (e.g.,
Aspergillus) are not an infection threat to healthy persons, but are a threat to
immunocompromised patients. In a through-the-wall air conditioner, for example, air
blowing through the coil during operation can disturb and aerosolize the water in its drip
pan; if the air-conditioner serves an isolation room, immunosuppressed patients could then
Another concern is that overflow from a drip pan can spill onto the floor,
creating a slip-and-fall hazard and adding to maintenance concerns (e.g., spill cleanup,
possible corrosion of the unit, possible mold growth in the unit's insulation).
- Ensure that drip pans are routinely maintained to
minimize the colonization and buildup of organisms and to minimize
condensate retained in the drip pan. For example, during annual HVAC
maintenance, clean the pans and ensure that the drains are open and flow
- Ensure that drip pans in such areas as isolation
rooms, intensive care units, bone marrow transplant units, operating rooms,
oncology suites, and respiratory therapy areas—where patients
susceptible to infection are likely to be found—drain to a sanitary
sewer to eliminate standing water. Also ensure that air from the drip pan
does not circulate to the patient area.
- Following construction and renovation projects,
thoroughly clean and sanitize HVAC units that have been exposed to dust,
dirt, and soil.
- Check that drip pans and drains are constructed to minimize problems
(e.g., are made from rust-resistant materials, use generously sized piping,
incorporate a drain trap). Local plumbing codes often define specific
requirements for condensate drains.
Cause of Device-Related Incident
External factor: Environmental
Mechanism of Injury or Death
Exposure to airborne infectious agents; Infection