for Cold Climate Housing and much more

Last Updated: , Created: Tuesday, January 15th, 2008

OVERVIEW: About cleaning up Mould.

The whole question of mould started as a simple nuisance in home maintenance but with experience and research has become a major element of creating and maintaining a healthy house. Of course, whenever research develops over time, recommendations change and things can get quite confusing.



Mould grows where there is constant moisture, warm temperatures and ideally something organic to feed on like wood, wallpaper glue or even the paper on drywall.  Although you are all aware that mould can even grow on ceramic tiles, not organic at all, if they are constantly wet.  Even if you clean-up mould, it will come back quickly if the moisture is still there to feed it. To avoid mould, or to prevent it from coming back after clean-up, you must control water leaks, control indoor humidity and find a way to warm up cold surfaces -- usually with either air sealing, insulation or air circulation. You need to avoid cold surfaces because they cause condensation, which is water, which grows mould. But let us concentrate here on cleaning. For many other aspects of mould, follow this link



One of the most common confusions is whether to use bleach or not to clean up household mould. You are right, bleach was recommended by everyone a few years ago, and in fact the standard formula was 8 parts water for 1 part straight laundry bleach. Today, bleach is not recommended in most cases of mould clean-up. Rather it is recommended to use unscented detergent and water, that's all. Why unscented? So that when it dries you can smell if there is still any mould that needs to be cleaned up, given that the human nose is incredibly skilled at detecting the presence of mould - that musty smell.

Bleach or other disinfectant may still need to be used if you are cleaning up a sewer back-up or a toilet overflow, something that has bacteriological contaminants in it. But bleach is now seen to be overkill for most needs, and dangerous to use.

Why is bleach dangerous? If you mix bleach with ammonia, it will produce a highly toxic gas - right in your face. Many household cleaners have bleach in them and many more have ammonia in them.  In addition, some types of mould react to bleach and give off toxic fumes as well - like as if they were defending themselves!  That is why government bodies have become worried about suggesting that people mix bleach with anything or even over use it on mould clean-up. TSP is a good unscented cleaner, but if concentrated, it is corrosive. Protect your skin and your eyes while working. Wear a mask as well to protect your lungs.  Unscented dish soap actually is a good product for cleaning up mould.



Why don't we need to kill the mould? For most of the mould in our houses, it is not the mould itself that bothers us, but by-products of the mould. Hence, dead mould can still raise havoc with allergies, because those by-products are not affected by the disinfectants. We have to clean-up and remove all traces of the mould. So a contractor who sprays something on the mould to kill it all but leaves it there is not doing the job that needs to be done.  Actually wiping off or scraping off the live or dead mould and getting it out of the house is what needs to be done.



For more details on the three categories of mould (allergen, infectious, poisonous), as well as the debate between the spellings of mould and mold, see "Just What Is Mould Anyway?".



Today's recommendations also make a distinction between when simple cleaning procedures that you can do yourself are adequate, and when the problem is so big that you and your house need protection from the cleaning procedure itself. Spreading massive quantities of mould spores all around the house is not a good thing. Generally if all the mould together is smaller that a patch 3 feet by 3 feet, it is felt that you can tackle it yourself with some basic precautions. If you use a vacuum cleaner, you must use a special HEPA filter or you will just be spewing fungal spores all over the house. Simply scrape it up, wipe it up, and dispose of everything including your mask and gloves and double wash your clothes by themselves. When there is more mould than three feet by three feet, or it is deep inside the walls, call in a professional who is specifically trained to deal with mould, protect himself and protect your house at the same time. 



Ideally you should clean-up and dispose of any mould even before drying the basement.  Why?  Because  mould can send out spores when it is wet or dry.  Massive use of fans before the mould is cleand up can just spread the problem.  Even with a fan in the window, it will be sending mould spores out the window and perhaps back into another window or a neighbour's window unless there is a HEPA filter on that fan. 



The proper sequence of flood clean-up is:

Pump out, vacuum and mop out the water;

Isolate the contaminated rooms sealing doorways and ducts, perhaps even create a bit of a negative pressure using HEPA filtered fans to the outdoors to prevent air movement from the basement into the rest of the house; 

Remove all contaminated building materials and contents to outside of the living spaces (not upstairs where they will just carry their contaminants); 

Remove all mould and clean the surfaces

Then start the drying process with dishumidifiers and fans exhausting outdoors to prevent the mould from coming back.


If getting to the mould, like in the walls, requires dusty demolition there are special precautions to take in addition to your own personal protection equipment.  Seal off the room where the dust will be created.  Plastic sheets with zippers are very useful for this.  Turn off the furnace and any ventilation device that could carry the dust to the rest of the house and put cloth or plastic over these grills.  Completely turn off the furnace and any whole house ventilation system and block all the air grills during the dusty portion of the demolition (don't forget to open the grills and turn it all back on when the dust and mould is gone as we need that heat to dry things out). 

If possible, put a fan in a window to draw air out of the area, but only if outdoors it does not blow into your neighbour's windows or ventilation ducts or back into your own.  Professionals have filtered vacuum trucks outdoors that depressurize the demolition room preventing contaminated dust from drifting back into the house or anywhere else.  Once the mould is totally cleaned up and you are simply in the drying stage, this can be simply an ordinary fan blowing out the window -- there should be no more contaminants to spread.



There is a standards group that has developed professional protocols for cleaning up mould and these are the basic references throughout North America: the Institute of Inspection, Cleaning and Restoration Certification standards body, the IICRC.  For assurance that a well meaning but untrained renovator does not miss some important part of these procedures that could end up impacting your own health, be sure that the professionals you hire to clean up mould have been trained and certified by the IICRC.



The 92 page Canadian bible on cleaning up mould was published by the CMHC in 1993 and revised and reprinted in 2004: "Clean-up Procedures for Mold in Houses". Unfortunately with the Conservative government's subsequent pull pack of research and even dropping the dissemination of good research information to the public, this essential publication was no longer available from CMHC, not even in "no-cost to the government" electronic format.  But the author of the publication has put it on-line and in the interest of Canadian's health, you can download it here.   Some of these old documents can now (2022) be found on the CMHC archive site.  Health Canada has picked up some of the slack with this information written for the serious mould problems in the First Nations communities up north.




Keywords: Condensation, Humidity, Mold, Moisture, Mould, Air Quality, Cleaning, Protection, Training, Environmental, Safety, Maintenance, Overview, Water, Health, Problems, Smell

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