The information we are providing in this article is based on current technical and scientific understanding of the topics discussed. Following the advice that is provided will not necessarily always provide total protection in every situation or against every health hazard that indoor air pollution causes.
When it comes to improving indoor air quality, there are three major strategies available:
- Air cleaners
- Improved ventilation
- Source control
The most effective method for improving indoor air quality usually is to get rid of individual pollution sources or reduce the emissions they produce.
Some sources, such as those containing asbestos, may be enclosed or sealed; others, such as gas stoves, may be adjusted in order to reduce the emissions. Source control is often a more cost-effective method to protect indoor air quality compared to increasing ventilation since that can increase energy expenses.
The most effective solution for a majority of indoor air quality issues inside a home is source control.
Another method is to reduce the concentrations of air pollutants inside the house is by increasing how much outdoor air comes inside.
A majority of residential HVAC systems, which include forced air heating systems, don’t introduce fresh air mechanically inside a home. You can increase the rate of outdoor ventilation by operating a window air conditioner while having the vent control open, running attic or window fans or opening doors and windows when the weather allows. Local kitchen or bathroom fans that exhaust outside to directly remove contaminants from the room with a fan helps to increase the rate of outdoor air ventilation as well.
It is especially important to take whatever steps you can when participating in short-term activities that may generate large quantities of pollutants – such as cooking, stripping, paint, painting, heating using a kerosene heater, or engaging in hobby and maintenance activities such as sanding, soldering, or welding. If possible and the weather allows you may want to do some of those activities outside.
Advanced designs in many new houses are beginning to come with mechanical systems that draw air from outside into the house. Some of those designs include heat recovery energy-efficient ventilators (also called air-to-air heat exchangers).
Shading and ventilation can help with controlling indoor temperatures as well. Ventilation helps to dilute or remove indoor airborne pollutants that come from indoor sources. That helps to improve the indoor air quality and reduces the number of contaminants. Be careful about using ventilation to decrease indoor air pollutants in situations where there might be outdoor pollutant sources nearby like refuse or smoke.
One of the most important factors to promote good air quality is to introduce outdoor air. There are several different ways that air can enter a house, including the following:
- via natural ventilation, such as via doors and windows
- via mechanical means, like through outdoor air intakes that are part of the HVAC system.
- via infiltration, which is a process where outside air flows into a home through cracks, joints, and openings around doors, windows, ceilings, floors, and walls.
Infiltration takes place to some extent in all houses.
Natural ventilation refers to air moving through open doors and windows. When used correctly, natural ventilation can sometimes help to moderate the temperature of the indoor air, which can become too hot inside houses that do not have air conditioning, or whenever a brownout or power outage limits or makes it impossible to use the air conditioner.
Natural ventilation may improve the quality of indoor air by reducing the levels of indoor pollutants. Natural ventilation examples include the following:
- window shading like closing the blinds
- opening doors and windows
A majority of residential forced air conditioning and heating systems do not mechanically bring air from outdoors into the house. Natural ventilation and infiltration are relied on to introduce air into the house. The advanced designs of many new homes are beginning to include a mechanical feature that introduces outdoor air via the HVAC system into the home. Some of the designs include an energy-efficient heat recovery ventilator to reduce the cost of heating and cooling the air during the winter and summer.
There are many different sizes and types of air cleaners that are available in the marketplace, which range from fairly inexpensive tabletop models to expensive and sophisticated whole-house systems. There are some air cleaners that are very effective at removing particles, while others are less so including a majority of tabletop models. In general, air cleaners are not designed for removing gaseous pollutants.
How effective an air cleaner will be will depend on how good it is at removing pollutants from the indoor air (measured in a percentage efficiency rate) and the amount of air that is drawn through the filtering or cleaning element (measured in the number of cubic feet per minute).
A highly efficient collector that has a low air-circulation rate won’t be effective, a cleaner with a less efficient collector and high air-circulation rate will not be either. Any air cleaner’s long-term performance will depend on maintaining it based on the directions provided by the manufacturer.
Another important factor that determines how effective an air cleaner can be is how strong the pollutant source is. In particular, tabletop air cleaners might not remove a sufficient amount of pollutants from nearby strong sources. Individuals who have a sensitivity to specific sources might discover that an air cleaner can be helpful only when they are combined with concerted efforts at removing the source.
There has been quite a lot of publicity over the past several years that laboratory experiments have shown that houseplants can reduce some chemical levels. However, there is no evidence currently, that a reasonable amount of houseplants remove high levels of pollutants in offices and homes. It is important to not over-water indoor houseplants since soil that is overly damp might provide microorganism growth which may affect people with allergies.
Using air cleaners to reduce radon levels and its decay products are not recommended by Environmental Agencies. The effectiveness of those devices is not clear since they just partially eliminate radon decay products without reducing the amount of radon that enters the house. The EPA is planning to do further research on whether or not air cleaners are currently, or could be in the future, a dependable way to reduce the health risk of radon.