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Indoor Air Quality Improvement Guide InspectAPedia®  -     Key strategies for Improving indoor air quality Removing or keeping out indoor contaminants Home ventilation strategies Best methods for cleaning & filtering indoor air

Here we provide a summary of common indoor biological contaminants such as mold, animal dander, pollen, viruses, and bacteria: remove these materials to improve indoor air quality in homes. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

Our page top photo shows an obviously moldy building that needs professional cleaning. But other mold and biological contaminants may be more difficult to spot. For help looking for less obvious indoor mold contamination see MOLD APPEARANCE - WHAT MOLD LOOKS LIKE. Also see ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings

© Copyright 2009 Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

A Quick Guide to Indoor Biological Pollutants

Our photographs above show common sources of indoor biological pollutants including an un-discovered sewage backup in a crawl space (above left) and cockroach fragments and fecal dust (above right). As reported in Best Practices Guide to Residential Construction:

Biological pollutants are or were living organisms. At least some of these are found in every home. Common examples include molds, pollen, dust mites, animal dander, and cockroaches, as well as viruses and bacteria. Our photos above show gross evidence of a sewer backup in a crawl space that was ignored by the building owner, leaving a pathogenic hazards in the building (above left), and a cockroach fragment found in building dust (above right).

Whether these biological hazards and particles are brought in to the building inadvertently by humans or pets or ride along on houseplants or their soil, living organisms tend to stay longer and breed more successfully in warm, damp conditions.

In fact, given temperatures of 50°F to 90°F and amaterial that stays wet for more than 48 hours, a colony of mold or other fungi will rapidly develop from their invisible spores, which are everywhere in our environment just waiting for the right conditions to spring to life.

Health Effects. Allergic reactions are among the most common health problems associated with indoor air quality. They are often connected with molds, pollen, animal dander (mostly from cats and dogs), and dust mites, which are microscopic animals living in carpets, bedding, and furnishings. Allergic reactions can range from annoying to life-threatening, as in a severe asthma attack. Common symptoms include watery, itchy eyes, runny nose, sneezing, nasal congestion, coughing and breathing difficulties, headaches, and fatigue.

Asthma. Children and adults with asthma are particularly at risk. Asthmatics have very sensitive airways that react to irritants by narrowing, making breathing difficult. Between 1980 and 1994, asthma rates in the United States rose by 75%, affecting over 20 million people today, including over 6 million children, according to the Centers for Disease Control and Prevention.

Our lab photo (left) shows skin cells and dog dander particles, dyed red with acid fuchsin for clarity.

Asthma “triggers” vary from person to person, but some of the most common indoor triggers are biological allergens, such as dust mites; molds; animal dander, urine, and saliva; and cockroach body parts, secretions, and droppings.

At ALLERGENS in BUILDINGS, RECOGNIZING we provide additional field and laboratory photographs of common indoor allergens.

Suggestions for Reducing Exposure to Biological Pollutants Indoors

Since most biological pollutants thrive in a moist environment, the key to reducing them is good moisture control. This starts with building houses correctly with good foundation drainage and waterproofing, proper flashings, continuous air and vapor barriers, and adequate ventilation. Household humidity levels should be maintained between 30% and 50%.

Basements should only be finished if they are dry year-round and detailed so finish materials and carpeting are not wetted by capillary action or condensation. If a building sustains water damage for any reason, it is essential that the wet materials be dried or removed within 24 to 48 hours or mold will grow. While wood, concrete, and other solid materials can be cleaned and disinfected, porous materials should be removed and replaced.

Hvac equipment and appliances that come in contact with water are other breeding grounds for biological contaminants. Have all such equipment serviced regularly and keep filters clean. Air conditioners can help filter out pollen, but dirty coils and drain pans can also become a source of biological pollutants. If using humidifiers, clean them according to manufacturers’ instructions and refill with fresh water daily.

Evaporation trays in air conditioners, dehumidifiers, and refrigerators should also be cleaned frequently. Duct cleaning may also be justified if an occupant is suffering from allergies and a visual inspection reveals that the air ducts are contaminated with large deposits of dust or mold. If so, choose a reputable company that follows the standards of the National Air Duct Cleaners Association (NADCA).

Good housekeeping is also an important part of the strategy for controlling household allergens. Bedding should be washed at 130°F. Using a HEPA vacuum or central vacuum with an exterior exhaust is recommended. Minimizing the use of carpeting, upholstered furniture, and dust-collecting shelving and furnishings can also help by eliminating hiding places for dust and contaminants (see Carpeting and Indoor Air Quality). In some case, portable or central air filtration may also play a role, but these are not a panacea for removing allergens (see Air Filtering Strategies).

-- Adapted with permission from Best Practices Guide to Residential Construction.

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• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
  Health Effects of Air Pollutants
  Common Indoor Air Pollutants
  Key Strategies for Improving Indoor Air Quality
  Whole House Ventilation Strategies
  Exhaust-Only Ventilation
  Supply-Only Ventilation
  Balanced Ventilation
  Air Filtering Strategies
  Particles in Indoor Air - Chart
  Quick Guide to Gases
  Air-Cleaner Types
  Air Filter Effectiveness
  Real-World Effectiveness of Air Cleaners
  Finding & Reducing Air Pollutants
  Radon Hazards
  Formaldehyde Hazards
  Biological Pollutants
  Volatile Organic Compounds VOCs
  Pesticide Exposure Hazards
  Lead Exposure Hazards
  Asbestos Exposure Hazards
  Carpeting and Indoor Air Quality
  Combustion Appliance Contaminants
  Backdrafting Appliances
  Fireplace & Woodstove Contaminants
  INDOOR AIR HAZARDS TABLE
  INDOOR COMBUSTION PRODUCTS & IAQ
INDOOR AIR QUALITY METHODS COMPARED
LEAD POISONING HAZARDS GUIDE
MOISTURE CONTROL in BUILDINGS
MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
MOLD ATLAS & PARTICLES INDEX
MOLD BY MICROSCOPE
MOLD CLASSES, HAZARD LEVELS
MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD
MOLD DETECTION & INSPECTION GUIDE
ODORS, Smells, Gases in Buildings-Diagnosis & Cure
RENTERS & TENANTS GUIDE TO MOLD
SEWAGE BACKUP TEST & CLEANUP
STAIN DIAGNOSIS
TECHNICAL & LAB PROCEDURES
THERMAL TRACKING
TRAPPED MOLD BETWEEN WOOD SURFACES
USING LIGHT TO FIND MOLD
VENTILATION in BUILDINGS
VINYL Siding or PLASTIC Window ODORS in Buildings
VINYL CHLORIDE HEALTH INFO
WATER ODORS

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Wiley.com and also at Amazon.com. See our book review of this publication.

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