Main content
City of Alexandria Homepage
City of Alexandria, VA City of Alexandria, VA
Health Department
Share Share RSS RSS Print Print Text Size Text Size NormalText Size LargeText Size Extra Large
Page updated Sep 29, 2011 12:34 PM

No Comments Posted Yet

Topic of the MonthFrequently Asked QuestionsSource Specific Controls


Respiratory Health and Indoor EnvironmentsWelcome to the Alexandria Health Department Environmental Health Division's "Respiratory Health and Indoor Environments" web site. Here you will find a wide range of information on the quality of your indoor air and its impact on your respiratory health.

This site covers the ins and outs of indoor air quality and informs you about what is being done to protect the health of residents living, learning and working in the City of Alexandria. This site aims to provide you with valuable indoor air and respiratory health information and guides you to other useful resources.

We invite you to browse and make inquiries.

Topic of the Month 

Habitat for Humidity

By David N. Easton
Certified Industrial Hygienist
Virginia Department of Health

“It is an accepted fact among Indoor Air Quality Experts that mold growth inside of a
structure is an indication that there are existing problems associated with moisture.”

Dr. Joseph Lstiburek
Building Science Consulting
70 Main Street, Westford, MA 01886

Indoor air practitioners are often contacted by potential clients who want them to “Come out and collect air samples to see what’s in the air I’m breathing in my home or workplace.” 

If you have made such a request, and the consultant has come to your site and performed these services without first trying to talk you out of it, you’ve probably contacted the wrong source.  Collecting air samples for mold or other indoor contaminants should probably be the activity of last resort when investigating indoor air quality problems.  Let’s examine the steps that should be taken to identify and arrive at a permanent solution to mold problems in occupied spaces. 

As the quote above indicates, mold growth and amplification is a symptom of an underlying moisture problem.  Even if you isolate and identify massive quantities of the nastiest fungi imaginable in the air or actively growing on structural components of your home or office, you can’t permanently eliminate them until you eliminate their fundamental growth requirements: food, air, and water.  The food, in this case, is the wood, paper, or other cellulose component of your structure; so you can’t very well remove these and retain the structure.  The air is a basic requirement for your continued survival.  That leaves the moisture component.  You can, and should consider excess moisture as the fundamental contaminant.

The Environmental Protection Agency has an informative web site ( that describes some of the things that you can do to eliminate moisture in your home and work environment to compliment cleanup efforts of existing mold, or to prevent its establishment.  Here are some of the things they point out:

  1. If you have a minor mold problem (usually defined as less than 10 square feet of growth on a cleanable surface), fix any leak or water problem first.  Then clean up the mold with soap and water and dry the surface thoroughly.  Note that there is no recommendation for the use of bleach or other disinfectant compounds. 
  2. If the mold is growing on a porous substrate such as carpeting, furniture, ceiling tile, or sheetrock, you are better off simply disposing of the material.
  3. If the growth is extensive (greater than 10 square feet) or the result of significant water damage, you are probably going to want to contact a professional remediation contractor.  Look under “Fire and Water Damage Restoration” in the yellow pages.  They have the capability to isolate the contaminated area to avoid spreading spores to adjacent occupied areas.  They can vacuum spores from contaminated surfaces with high efficiency (HEPA) filtered vacuum cleaners, and provide the appropriate follow-up activities to make the space suitable to be reoccupied.
  4. Reduce the relative humidity within your space (less than 60-65% is your target value) to minimize the chance of establishing mold growth on surfaces.  Do so by venting bathrooms, clothes dryers, cooking exhausts, and other moisture producing operations directly to the outdoors.  Use air conditioning or dehumidification devices in a manner that reduces moisture content.  For example, an air conditioning unit that is oversized for the space it serves will not dehumidify effectively because it doesn’t have to work hard to cool.  It, therefore, doesn’t operate long enough to wring sufficient moisture from the ambient air. 
  5. Prevent condensation from occurring on cold surfaces such as windows, exposed pipes, ducts, and exterior walls.  Install insulation and consult with a building engineer regarding the proper orientation of vapor barriers associated with the insulation used.
  6. If flooding occurs, clean and thoroughly dry wet materials or furnishings within 24-48 hours to prevent mold growth.
  7. Clean and repair roof gutters regularly.  Extend downspout discharge points away from the building foundation.  Grade soil aroung your foundation so that it slopes away from the building so that water does not collect and penetrate the foundation.
  8. Keep air conditioning drip pans clean and the drain lines unobstructed and flowing properly.

Always remember that mold and fungi are everywhere in our environment, and life would not be possible without them.  But you can and should take steps to minimize their growth indoors.  The only practicle way to do so is to eliminate the extraneous sources of moisture and humidity that they require.

Subject of Interest & Frequently Asked Questions 

Source Specific Controls