Steps To Prevent Mold in Workplace Air Conditioning Systems and Buildings,
as recommended by the U.S. Occupational Safety and Health Administration
Preventive Maintenance: Preventing mold growth in occupied areas
The key to mold prevention is moisture control. The most important initial
step in prevention is a visual inspection. Regular checks of the building
envelope and drainage systems should be made to assure that they are in
working order. Identify and, to the
extent possible, eliminate sources of dampness, high humidity, and moisture
to prevent mold growth.
Wet or damp spots and wet, non-moldy materials should be cleaned and dried
as soon as possible (preferably within 24 to 48 hours of discovery).
Moisture due to condensation may be prevented by increasing the surface
temperature of the material where condensation is occurring, or by reducing
the moisture level in the air (humidity).
To increase the material's surface temperature, insulate it from the colder
area or increase air circulation of warmer air. To reduce the moisture
level in the air, repair leaks, increase ventilation (if outside air is cold
and dry) or dehumidify (if outside air is warm and humid). Indoor relative
humidity should be maintained below70% (25-60%, if possible)
All buildings should be checked routinely for water leaks, problem seals
around doors and windows, and visible mold in moist or damp parts of the
building. Any conditions that could be causes of mold growth should be
corrected to prevent future mold problems.
Other prevention tips include venting moisture-generating appliances, such
as dryers, to the outside where possible; venting kitchens (cooking areas)
and bathrooms according to local code requirements; providing adequate
drainage around buildings and sloping the ground away from the building
foundations; and pinpointing areas where leaks have occurred, identifying
the causes, and taking preventive action to ensure that they do not reoccur.
Preventing mold and bacterial growth in the building's ventilation system
Ventilation systems should be checked regularly, particularly for damp
filters and overall cleanliness. A preventive maintenance plan should be put
into place for each major component of the building's ventilation system.
Contact your equipment supplier or manufacturer for recommended maintenance
schedules and operations and maintenance manuals. Components that are
exposed to water (e.g., drainage pans, coils, cooling towers, and
humidifiers) require scrupulous maintenance to prevent microbial growth and the entry of undesired microorganisms or chemicals into
the indoor air stream.
Cleaning the building's air ducts
Air duct cleaning generally refers to the cleaning of various heating and
cooling system components of forced air systems. The components of these
heating and cooling systems may become contaminated with mold if moisture is
present within the system, resulting in the potential release of mold spores
throughout the building. All components of the system must be cleaned.
Failure to clean a component of a contaminated system can result in
re-contamination of the entire system. Water-damaged or contaminated
porous materials in the ductwork or other air handling system components
should be removed and replaced . Ventilation system filters should be
checked regularly to ensure that they are seated properly. Filters should be
replaced on a routine schedule.
Source: U.S. Occupational Safety & Health Administration, in its publication
No. OSHA 3304-04N2006Preventing Mold-Related
Problems inthe Indoor
Guide for Building Owners,
Managers and Occupants