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Indoor air quality and mold prevention guidelines

Indoor air quality and mold prevention guidelines

The quality of the air in your home can impact your health or the health of those you live with. Most people are aware that outdoor air pollution can significantly affect people's health, but Environmental Protection Agency studies have shown that levels of air pollutants indoors may be anywhere from 2 to 5 times greater than outdoors, and in some cases more than 100 times greater.

Indoor air pollution can be a real concern because people can spend as much as 90% of their time indoors, and much of that time is in their homes. You can have an immediate or long-term reaction to poor indoor air quality.

One way to determine whether you have an indoor air quality problem is to look at how you or those in your household feel when home.

  • Do you or others sneeze and cough in your home?
  • Do you or others in your home wake up congested or with a headache?
  • Do you or others in your home often have an irritated throat, nose or eyes?
  • If you or others in your home have any of the above symptoms, are they more common in a certain part of the house?
  • Does anyone in your home have frequent asthma episodes or respiratory infections?
  • Do you notice that you feel better when you are away from home?

If you have answered "yes" to any of these questions you may have an indoor air quality concern.

  • Smoking indoors, smoke drifting in from outdoors, or smoke being carried indoors on clothing
  • Other things that burn, like oil, gas, kerosene, charcoal briquettes, wood or candles
  • Central heating, cooling or humidifying systems
  • New or recently installed building materials and furnishings, including carpets and certain wood pressed products
  • Household cleaning and maintenance products
  • Personal care products, like hair spray or soaps
  • Too much moisture in the house
  • Tracking pesticides and pollens in on shoes and clothes
  • Improper circulation of fresh, outside air
  • See mold resources website by the EPA

The health or quality level of the air in a home is determined by how much and how often pollution is getting into the air. For example, if you have a properly adjusted gas stove, it will emit significantly less carbon monoxide than one that is not properly adjusted. Also, good ventilation contributes to improving air quality:

Managing biological and chemical pollution factors, like pesticides and mites

  • Don't smoke indoors.
  • Circulate fresh, outdoor air through your home every day to remove stale air and move pollutants out.
  • Wipe feet off before coming inside, and take shoes off in the house in order to keep out pesticide contamination.
  • Replace or clean furnace and air filters when they are dirty. Check them regularly, at least every two months. Use a "high efficiency particulate filter" (HEPA).
  • Use ventilating fans over the stove and in the bathroom and be sure they are vented to the outside of the house.
  • Keep ventilating fans clean.
  • If you have mold, or areas that develop mold, see the section below titled, "Keeping your home healthy and free of mold during the wet seasons."
  • Use safe cleaning products, those without any of the signal words ("danger", "warning" or "caution"). If you do not use safe household products, read the label and follow the directions carefully.
  • Vacuum carpets well and stuffed furniture well, wash linens weekly and dust regularly to keep the allergen "dust mites" to a minimum. Dust mites are microscopic bugs that live in the dust and our sloughed off skin.

Managing combustible pollutants in your home, like natural gas

  • Don't smoke indoors.
  • Assure the gas flame in all appliances is blue, without much yellow. If there is a strong smell of natural gas, open the windows, leave the house, and call the gas company.
  • Be sure to have good ventilation in rooms with working fireplaces and gas or wood stoves.
  • Do not burn charcoal or kerosene heaters indoors. See carbon monoxide facts.

Mold is a form of fungi. Mold is found in every moist indoor and outdoor environment year round. It grows naturally indoors, and can also enter your home on shoes, clothing, bags, animals, windows and ventilation systems. There is always a little mold in the air and on many surfaces. The mere presence of molds does not necessarily lead to symptoms. Mold may become a problem where there is excessive moisture, such as leakage in roofs, pipes, walls, plant pots, or where there has been flooding.

In King County, the wet seasons of fall, winter, and spring can mean more moisture in your home. Too much moisture can lead to mold and mildew. Although mold exposure does not always cause health problems, daily exposure has been known to cause respiratory problems, headaches, watery eyes, dizziness, lethargy, rashes and other reactions. Mold and other biological contaminants can trigger asthma, too.

Here are some suggestions to keep your home clear of molds:

Get excess moisture out of your home

  • Flush the air two or three times a day (for three to four minutes, open all the doors and windows and let fresh air circulate through the home).
  • Ventilate the bathroom and the kitchen with an exhaust fan.
  • Keep shower curtain or bathtub sliding door open after bathing to increase air circulation.
  • Assure that the dryer vents freely to the outside.
  • Heat all the rooms in your home to keep moisture from forming on the walls and other surfaces of unheated areas.

Stop moisture from coming in

  • Stop any leaks from the roof, poorly-drained gutters and plumbing.
  • Stop water from entering basements and crawlspaces.
  • Properly insulate walls and ceilings.
  • Grade ground so that it drains surface water away from home.

Other preventive measures

  • Use easy to clean paint and wallpaper, especially in bathrooms.
  • Install a timer switch on your bathroom fan, and leave the fan on for 15 minutes after showering.
  • When cooking, try to minimize simmering of liquids and foods.
  • Keep furniture away from outside walls where mold might grow.
  • Replacing carpet with wood or vinyl floor tiles will prevent some of the problems with carpeting.

Steps to clean up mold in the home

Use the following guidance to clean small areas of mold in the home (less than about ten square feet or a 3 feet by 3 feet patch). Get professional help if the mold growth covers more than 10 square feet. More information is available from EPA's website.

  1. At a minimum, wear an N-95 mask (available at hardware stores), disposable gloves, and goggles when cleaning up mold.
  2. Wash moldy surfaces with a mild detergent solution, such as laundry detergent or dish soap and warm water. Products with an EPA Safer Choice label are the best choice. Go to the Safer Choice website and find a product under either Laundry Products: Laundry Detergent or Dish Soaps. Select a Fragrance Free product, if you prefer. EPA Safer Choice products have been tested for performance and are the safest in their product class.
  3. Throw away materials that cannot be cleaned or are too damaged to reuse. Porous materials, like ceiling tiles, likely cannot be cleaned thoroughly and should be discarded.
  4. The use of bleach is generally not recommended, unless a sewage release has occurred. If you must use bleach, wipe the surface with a solution of 1/4 cup bleach to one gallon of water. Wait 20 minutes and repeat. Wait another 20 minutes. Never mix bleach with ammonia or other cleaners because fumes from the mixture are harmful.
  5. After cleaning, rinse the surface with clean water.
  6. Dry surfaces quickly and thoroughly after cleaning. You can use a fan, air conditioner or dehumidifier.

Tenant/renter responsibilities

As a renter, you must control condensation in your home to prevent mold growth. See the section above for guidance. You also must notify your landlord, in writing, or any water leaks or moisture problems as soon as you notice them.

Landlord responsibilities

As a landlord, you're responsible for maintaining the rental unit. You can do this by:

  • Notifying tenants of the health hazards related to mold exposure and how to prevent mold growth.
  • Fixing any water leaks, moisture problems, and any ventilation or heating issues that may lead to moisture problems.

Resources for low-income renters

For free legal help, counseling, and representation for low-income renters:

For housing counseling services, best practices, and FAQs about landlord-tenant laws:

For complaint inspections:

Resources for renters with asthma

  • King County Weatherization Program: Get help with ventilation improvements and other weatherization for your home by applying to this program from King County Housing Authority. Any home can apply but those with respiratory issues such as asthma or COPD are given priority.
  • King County Community Health Worker Program: This program provides free virtual home visits to King County residents with asthma. They also provide educational materials and supplies such as HEPA vacuums and air purifiers.
  • UW Pediatric Environmental Health Specialty Unit: Provides information and guidance for those with reproductive or pediatric environmental health concerns. Consultations are free, and most are over the phone and email. They may recommend a clinic appointment. Financial help is not available for clinic appointments through this group.

Resources for landlord-tenant disputes

The state Residential Landlord-Tenant Act (RCW 59.18) explains the rights and responsibilities of landlords and tenants. When it comes to mold, the act states that “Your local building and code enforcement officials may take action is building problems are not addressed – they won't respond to mold complaints, so it's important to stress the source of the water problem.”

Contact your local building or code enforcement official to report an unaddressed water or maintenance issue. Here are additional resources:

Public Health does not conduct mold assessments. If you would like more educational resources, please fill out our mold assistance request form. If you need a mold assessment, visit the American Industrial Hygiene Association's consultant directory.

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