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| Water and nutrients offer a fertile breeding ground for mold. Flood damage should be repaired or replaced as soon as possible to prevent cross-contamination. |
Mold, or fungi, lives in virtually any building, under sinks, in bathrooms, basements, refrigerators, or any damp dark place. At first, the mold is inconspicuous, or microscopic. After it has spread and completely covered the area with millions of cells, you start to see the mold.
When considering mold, air filters serve the purpose of limiting the amount of spores in a given volume of air thus limiting the reproduction capabilities of the mold. Mold needs three things to survive, appropriate temperatures, nutrient (food sources), and water. All three of these items are indigenous to an HVAC system. Typical HVAC system temperatures range from 85° F to 140° F. Airborne contaminants, including molds, can become nutrients for other airborne molds, and water may be common in the area of coils or actually introduced through humidifiers.
Proper application of Heating, Ventilation and Air Conditioning (HVAC) components per ASHRAE[1] recommended practices serves to limit the possibility of contaminant growth within a system. The two most important considerations are the removal of contaminants (nutrients) and moisture. The presence of mold in buildings is becoming more common due to more airtight construction practices that improve insulation and energy efficiency but precipitate moisture in walls and ceilings.
Mold spores are well over one-micron in size and easily removed by applying air filtration according to ASHRAE recommendations. Even a MERV[2] 6 pleated panel filter will have an efficiency against most molds of over 80%. One key consideration is that air must be moved through the filter for the filter to remove the contaminants. If elevated mold contamination levels are suspected, increasing the air changes to the space may have a debilitating effect on the mold’s reproduction. As more air is moved through the air filter the total space contaminant removal efficiency is increased.
If a health situation exists specific to a species of mold the application of proper air filtration with appropriate air conditioning system operation can severely reduce exposure. Some mold requires a higher level of filtration efficiency for removal because of its smaller particle size. The chart on the mold filtration recommendations page lists some common mold species and the filter efficiency that should be applied.
The most important component of control is the limitation of water in the environment and in the HVAC system. ASHRAE recommends that spaces have a controlled humidity level of under 60%. Consistently exceeding this level is a prescription for problems. Try placing a slice of bread in a dish with some water next to a slice of bread on a dish alone and watch the result.
To prevent mold proliferation in your building:
· Reduce indoor humidity by:
o Maintaining building under positive pressure (keeps moisture and nutrients outside the building in their natural environment)
o Following ASHRAE HVAC system design guidelines (30% to 60% RH maintenance)
o Vent moisture producing sources to the outdoors (locker room exhaust, bath exhaust, cooking exhaust)
· Controlling growth at the source:
o Look for and correct the cause of water stains on ceilings, walls and floors
o Assure plumbing fixture integrity
o Assure that all HVAC drain pans are sloped properly and that drains are free of obstruction
o Inspect HVAC equipment periodically for sources of contaminant or moisture buildup
o Eliminate all sources of condensation, windows, piping, etc.
o Seal penetrations in walls or floors, especially below ground
o Check for moldy odors
o REMOVE ANY SOURCE OF FREESTANDING WATER.
If mold is discovered, fix the source of the problem. In most cases, the best level of control of contaminated materials is the complete removal of the contaminated items. This includes completely replacing wallboard, sheet rock, and carpeting or damaged organic materials (wood bearing products). Light instances may be cured using a weak bleach solution. In this case, you must assure that the contaminated item be allowed to dry completely.
The control of mold in our environment requires diligence and the application of good building and HVAC system housekeeping. The key to air quality control in any application is to maintain contaminant dosage at acceptable levels, whether the level is sensory or definitive based upon a health guideline. Air filtration always plays a major role in this arena.
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