Clean, Clean, Clean
The appropriate cleaning of your hurricane damaged possessions and home depends on a number of factors. Was the water that entered your home contaminated or clean? Did the water "flood" into your home or did it enter from the torrential rains? Did the water bring mud, silt or other organic material into your home?
According to the Institute of Inspection Cleaning and Restoration Certification S500 Standard and Reference Guide for Professional Water Damage Restoration, Falling rain water is an example of clean water. Whereas water from "wind-driven rain from hurricanes, tropical storms or other weather-related events" may "carry silt, organic matter, pesticides, heavy metals, regulated materials , or toxic organic substances." During an emergency such as has occurred with Hurricane Harvey, it may not always be practical to make a definitive decision about the exact nature of the water.
If you can see dirt or silt that has entered your home along with the water, there is a good chance it has various forms of contamination.
If your home has remained wet for more than a few days or there is a foul odor, then the water may have deteriorated and allowed bacteria to grow.
If there is any doubt about the level of contamination in the water that entered your home, it is likely best to treat it as contaminated.
Many people immediately begin spraying chemical biocides as soon as they can return to the building to begin the clean-up process. Unfortunately, when contaminated water is present, the biocides are going to be almost immediately inactivated by the presence of dirt, silt and organic matter. One of the greatest risks of this is there will be an assumption that the organisms have been killed and the area has been disinfected and is safe, when in fact it is not safe! Over the last 30 years of my consulting work I have tested over a thousand homes that have been contaminated with varying amounts of sewage. What is clear from my practice and from published literature is that the initial application of a biocide is not effective in making buildings safe from harmful micro-organisms. If you carefully read the label for biocides such as chlorine bleach they clearly state that the product is for use on clean or pre-cleaned non-porous surfaces. Biocides such as bleach, peroxide, quaternary ammonium compounds, iodine etc. will not be effective at disinfecting contaminated items such as:
Wall or ceiling gypsum board
or other highly porous construction materials
When these porous materials get wet with contaminated water they will hold contamination so that they can not be safely cleaned. This is one reason they need to be removed and discarded. Another is that they hold a lot of water and will slow down the drying process for the rest of the materials which can be effectively cleaned.
The best cleaning solutions are soap and water or detergent and water. The surfactant action of cleaning agents will go a long way toward killing the bacteria by causing their cell membranes to rupture. But that is not enough. The organisms whether they are alive or dead need to be physically cleaned from the environment. Killing gram negative bacteria, which are common in sewage and silt contaminated water, and leaving their dead bodies around can result in high levels of endotoxins which are toxic compounds that can cause flu-like symptoms at relatively low levels of exposure. Other gram positive organisms such as Clostridium tetani are also common in flood waters. Gram positive organisms can also be disease causing and release exotoxins. It is the physical removal of the dirt, silt, bacteria, mold and other flood related contaminants that makes the difference.
If the flooding has resulted in silt, dirt and fine debris:
Make sure you are wearing the proper protection. Large quantities of dirt, silt and debris can be removed with a shovel.
Smaller quantities can be hosed out while the building is still wet. (avoid using a high pressure hoses to prevent splashing and aerosolization).
Silt and contamination that has gotten into wall cavities and under sill plates should be flushed out with a "Hudson" type sprayer using a soap or detergent solution until the water flushes out clean. (avoid high pressure washing to avoid slashing and aerosolization). The water is flushed under or behind the sill plates and immediately collected with a HEPA shop vacuum or cleaned up as best as possible. If you aren't using HEPA the contaminants are likely to be aerosolized further.
Mops tend to spread and smear contaminants around instead of picking them up. When you dip a dirty mop into a bucket of cleaning solution - the solution becomes contaminated. To get things really clean after the bulk of the filth has been removed stick to extraction type cleaning systems or use disposable type wipes such as Swiffer, Rubbermaid or Bona disposible floor cleaning wipes.
You can tell when the surfaces are clean by using a clean towel or cotton swab to check. Keep cleaning with the soap and water until it really is clean.
Extract or clean up any excess water so the surfaces don't have standing water.
After everything is clean - you can apply the biocide to the cleaned surfaces. Don't spray biocide on mold growth (this will be my next blog topic).
Biocides require a "dwell time" in order to be effective. Typically 15 minutes to 30 minutes.
A single application is rarely enough. After waiting for the necessary dwell time, clean up any residual biocide then reapply a second time and wait another 15 to 30 minutes.
Never, Never, Never! mix biocides unless the label directions specifically recommend it. At best mixing with incompatible chemicals will make the biocide ineffective. At worst it will release toxic gases that kill people every year! An example of a deadly combination is bleach and ammonia. Mixing these together produces deadly fumes!
For emergency water damage work chlorine bleach is a good choice. It is cheap and effective, but only if it is used as directed on the label.
The label directions for most biocides call for rinsing afterward with water. Many biocides like chlorine bleach are corrosive to metals and can leave noxious residues.
Once the areas are clean and treated they need to be thoroughly dried before reconstruction. If mold has been present - don't put the area back together yet.
There are a variety of tests that can be performed to check to see if disinfection has been adequate and successful, but the most important clue that contamination from microorganisms has been taken care of is the surfaces are really clean. You should be able to wipe Swiffer wipe or other microfiber type cloth over about 40 square feet and have it look clean. A little dingy is okay - but it shouldn't look dirty.
Tomorrow's blog with be about mold that can develop after flooding event. Make sure to check back for this important information.