ICS Magazine

Equipment Decontamination on Water Losses

April 12, 2007


Frequently, questions arise regarding cleaning and decontaminating equipment following a water loss. If the loss is a Category 1 or 2, is there still a need for decontaminating equipment that was used there?

Most homes and commercial buildings have contaminants present in carpet and on flooring, and those contaminants are easily aerosolized with the movement of the air velocity created by air movers. After being aerosolized, those contaminants may be deposited both in and on the equipment, creating the necessity of cleaning and decontamination.

Arguably, all equipment used on water losses, indeed equipment used in any high-humidity situation for an extended period, should be cleaned before storage to prevent microbial growth and potential contamination of subsequent jobs on which they are used. Even the portable hot water extraction equipment used to clean carpet – at least the recovery tank – requires flushing and cleaning at the end of the day to prevent discharge of contaminants collected from the previous day’s work.

However, you should consider the definitions of the Categories of Water contained in IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration (Categories 1-3; clean source, contaminated, grossly contaminated), along with the conditions for microbial germination, growth, amplification and dissemination before arriving at blanket decisions that have productivity and cost consequences for both the water restoration contractor and customer.

Let’s take a moment to review the conditions required for the microbial growth and amplification
  1. Organic food source, especially cellulose
  2. Moisture, generally 16 percent MC in structural wood or 67 percent ERH on organic surfaces
  3. Temperature range of 68-86F (20-30C); 78F or 25C being optimum for most common household molds
  4. Stagnant air
  5. Time of two to three days to germinate under optimum conditions for common household molds (e.g., Aspergillus, Penicillium sp.)


In most cases where airmovers and dehumidifiers are used, Category 1 water losses, along with structural and contents surfaces, are subject to rapidly moving air, often coupled with high temperature extremes, or perhaps even evaporative cooling during the latter stages of drying when temperature moderates. Closed-chamber studies conducted by Research Triangle Institute demonstrate that cellulosic ceiling tiles that are inoculated with Penicillium mold and are wet do not support microbial amplification in atmospheres <85 percent RH where air movement is present. Considering that equipment components are inorganic, that components get quite warm or hot (sometimes cold) during operation, and that most produce quantities of circulating air, it is therefore highly unlikely that they will support microbial growth. If they do, it probably will be on organic soils collected on filters, or on coil fins or fan blades.

Additionally, the target relative and specific humidity recommended on water losses within the first 24 to 48 hours is 40 percent RH or 40 gpp, which in most cases is insufficient to support microbial growth, especially in a non