Day 4: On all things MOLD….

Mold spores

Fun quote of the day:

“In the UK, I feel that nose hairs are seen as a far cheaper option than replacement filters…” – British indoor air consulting colleague, overheard at breakfast

Today, I attended a number of technical sessions about mold — new approaches, health perspectives, and most importantly, comparisons of which techniques work the best.  Here are a few factoids to share (some basic, others new even to me):

  1. Why does mold grow? Mold spores exist everywhere — they naturally are produced by fungi outdoors and then waft indoors with natural air movement.  However, they grow rapidly and reproduce, emitting hundreds of thousands of spores that can cause health problems, when conditions are right.  This means oxygen, moderate temperatures, something to eat (virtually anything, including the oil from our fingerprints), and most importantly, moisture.  Moisture is the only one out of those elements that we can really control, so it’s the key to preventing or stopping mold growth indoors.
  2. Why does mold often grow around windows? Since mold loves water, look for areas that are damp or unventilated.  Windows often get wet during the winter because when the moist indoor air contacts the cold surface of glass or metal frames (thermal bridges), the moisture in the air condenses out of the air into water droplets on the cold surface.  This moisture, then diffuses to nearby porous areas like curtains and painted windowsills, where mold spores can happily begin growing.
  3. How come mold affects some people and not others? Whether you react to mold is based on whether you are allergic to it.  It’s estimated that about 25% of people are allergic to mold and there is a genetic linkage to this — if your parents are allergic, you have a higher chance of being the same way.  Dosage is also a factor — for some people, a small amount of mold won’t cause problems, but beyond a certain threshold, the effects come on quickly.
  4. Why is allowing children to be around mold a bad idea? Mold is an allergen that can be sensitized.  Sensitization is the process by which the human body recognizes that something is an allergen.  When it realizes this through long-term exposure, the body starts to take defensive action — puffing up nasal and throat passages (stuffed respiration), eye watering, sneezing, elevated blood pressure, headaches.  No one seems to know exactly how long this sensitization takes, but once you develop an allergy, it is with you even once you leave an environment with that allergen.  In other words, it’s permanent.  If that wasn’t enough, a 3-year long study by the World Health Organization (WHO) concluded that children in homes with mold and dampness had a 30-50% higher incidence of asthma.
  5. How do I avoid having a moist environment? First, “moist” means anything above 55% relative humidity (according to ASHRAE).  Lots of things we do add moisture to our living spaces: bathing, cooking, plants, clothes drying, floor heating instead of air conditioning, leaking of water from outside into the indoors, even just people breathing.  One interesting fact was that 200 liters of water can penetrate over a year through a 1/2″ hole.  Be aware of sources, use exhaust fans and dehumidifiers to remove moisture (contact us to find out which ones we like and why).
  6. Can I fix my own mold problems? The conventional wisdom (that we ourselves at PureLiving have been advising) is that in general, areas with mold of less than 1 square meter can be cleaned up by the homeowner instead of professionally.  When we do home mold inspections, we often provide a protocol on how to do this.  However, today, I attended a case study session where a professional mold remediator from New York compared mold spore counts under a variety of conditions — do-it-yourself (with  few containment measures to reduce cross-contamination), vs. use of engineering controls (filters, negative pressure), and vs use of good work practices (using bags, HEPA vacuuming, and other standard practices pros follow).  The findings?  Under the DIY conditions, spore counts were nearly 20x higher, both in the immediate work area and in adjacent rooms. This was not surprising, but no one had ever actually quantified this.  This means that the next time your landlord sends over someone with a chisel to scrape the mold off your wall, you should tell him to take a pass.
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