As stated by the ACGIH, “any remediation plan attempt that does not include long-term plans to maintain systems and prevent recurrence is short-sighted and destined to fail. There is no one-time, complete “cure" to microbial contamination within structures. Rather, continued oversight and attention to conditions that may allow microbial growth must become an integral part of the control plan." Once remediation efforts have been conducted, three basic strategies should be implemented: (a) routine surveillance inspections and prompt response to problems, (b) adequate preventative maintenance of the building structure, as well as, HVAC and plumbing systems, and (c) adequate housekeeping including an emphasis on proper and routine cleaning.
The EPA recommends that the Relative Humidity (RH) levels in the living spaces are maintained between 30% - 50%. Relative Humidity levels that exceed 50% can influence dormant mold to grow or may promote favorable conditions for new mold growth. It is further recommended that RH levels do not go below 30% as that may cause an uncomfortable living environment.
Indoor temperatures also are a factor that is considered for mold growth. When temperatures exceed 85° F or 29.5° C mold can start to flourish. Mold growth is slower at colder temperatures and at 32° F or 0° C mold colonies will go dormant. If temperatures and RH are not controlled, dew points (condensation) can be reached. This will allow moisture to be present on or under surfaces which can cause the start of mold. For example if an indoor temperature in a room is 80° F, the RH is 75% and the outdoor temperature is 45° F, the exterior walls may achieve dew point and start to sweat. This example can also be reversed. If the outdoor temperature is 90° F, the RH is 70% and the indoor temperature is 60° F, the same occurrence can happen. It is recommended as a guideline by American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) that indoor temperatures in the winter months are maintained between 68° F -75° F (20° C - 24° C). During the summer months it is recommended as a guideline that indoor temperatures are maintained between 73° F - 79° F (23° C - 26° C).
It is important to note that the cause of any mold growth needs to be identified, corrected and the mold/mold contaminated materials be appropriately cleaned or removed. IICRC S520 Standard and Reference Guide for Professional Mold Remediation states the use of detergents, antimicrobials, Ozone, heat treatment or other biological controls used in killing mold as a stand-alone method, has not been shown to eliminate the contaminants nor their potential allergenic or toxigenic properties.