Biocide Use: " Remediatiors must carefully consider the necessity and advisability of applying biocides when cleaning microbially contaminated surfaces. The goal of remediation programs should be removal of all microbial growth. This generally can be accomplished by physical removal of materials supporting active growth and thorough cleaning of non-porous materials. Therefore, application of a biocide would serve no purpose that could not be accomplished with a detergent or cleaning agent. Prevention of future microbial contamination should be accomplished by (a) avoiding the conditions that led to past contamination, (b) using materials that are not readily susecptible to biodeterioration, and (c) where necessary, applying compouds designed to suprress vegetative bacterial and fungal growth or using materials treated with such compounds." Edit Text

HVAC System Remediation: "Non-porous materials can be readily cleaned and reused. Application of biocides as a substitute for removing microbial growth and settled biolocical material is not considered acceptable. In the first place, most dis-infectants and sanitizers are approved for use on previously cleaned rather than soiled surfaces. Secondly, the allergenicity and toxicity of biological material is not related to microorganism viability. Contaminated porous materials in HVAC systems must be removed to the bare (underlying) metal and the contaminated materials appropriately discarded. Full-containment procedures should be implemented when removing extensive areas of contaminated porous materials from large HVAC system components (e.g., air handling plenums). Depending on the extent of visible fungal contamination, removal of porous materials from smaller HVAC system components (e.g., unit ventilators and fan coil units) requires source or local containment precautions supplemented by HEPA vacuum cleaning."

Source - Bioaerosols: Assessment and Control

Molds live in the soil, on plants, and on dead or decaying matter. Outdoors, molds play a key role in the breakdown of leaves, wood, and other plant debris. Molds belong to the kingdom Fungi, and unlike plants, they lack chlorophyll and must survive by digesting plant materials, using plant and other organic materials for food. Without molds, our environment would be overwhelmed with large amounts of dead plant matter.

Molds produce tiny spores to reproduce, just as some plants produce seeds.   These mold spores can be found in both indoor and outdoor air, and settled on  indoor and outdoor surfaces. When mold spores land on a damp spot, they may begin growing and digesting whatever they are growing on in order to survive.  Since molds gradually destroy the things they grow on, you can prevent damage to building materials and furnishings and save money by eliminating mold growth.

Moisture control is the key to mold control.  Molds need both food and water to survive; since molds can digest most things, water is the factor that limits mold growth. Molds will often grow in damp or wet areas indoors. Common sites for indoor mold growth include bathroom tile, basement walls, areas around windows where moisture condenses, and near leaky water fountains or sinks. Common sources or causes of water or moisture problems include roof leaks, deferred maintenance, condensation associated with high humidity or cold spots in the building, localized flooding due to plumbing failures or heavy rains, slow leaks in plumbing fixtures, and malfunction or poor design of humidification systems. Uncontrolled humidity can also be a source of moisture leading to mold growth, particularly in hot, humid climates.

Health Effects and Symptoms Associated with Mold Exposure:

When moisture problems occur and mold growth results, building occupants may begin to report odors and a variety of health problems, such as headaches,  breathing difficulties, skin irritation, allergic reactions, and aggravation of asthma symptoms; all of these symptoms could potentially be associated with mold exposure.

All molds have the potential to cause health effects. Molds produce allergens, irritants, and in some cases, toxins that may cause reactions in humans. The types and severity of symptoms depend, in part, on the types of mold present, the extent of an individual's exposure, the ages of the individuals, and their existing sensitivities or allergies. 
 

Ten Things You Should Know About Mold:

1. Potential health effects and symptoms associated with mold exposures include allergic reactions, asthma, and other respiratory complaints.  

2. There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to control moisture.

3. If mold is a problem in your home or school, you must clean up the mold and eliminate sources of moisture.

4. Fix the source of the water problem or leak to prevent mold growth.

5. Reduce indoor humidity (to 30-60% ) to decrease mold growth by: venting bathrooms, dryers, and other moisture-generating sources to the outside; using air conditioners and de-humidifiers; increasing ventilation; and using exhaust fans whenever cooking, dishwashing, and cleaning.

6. Clean and dry any damp or wet building materials and furnishings within 24-48 hours to prevent mold growth.

7. Clean mold off hard surfaces with water and detergent, and dry completely. Absorbent materials such as ceiling tiles, that are moldy, may need to be replaced.

8. Prevent condensation: Reduce the potential for condensation on cold surfaces (i.e., windows, piping, exterior walls, roof, or floors) by adding insulation.

9. In areas where there is a perpetual moisture problem, do not install carpeting (i.e., by drinking fountains, by classroom sinks, or on concrete floors with leaks or frequent condensation).

10. Molds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present. There are molds that can grow on wood, paper, carpet, and foods.

EPA Publication:

"A Brief Guide to Mold, Moisture, and Your Home"

http://www.epa.gov/mold/moldguide.html