For many people, the health risks posed by indoor air quality can often be significantly higher than outdoor air. Animal dander, pollen, mold, dust mites and fumes released by cooking, burning fuel or cleaning products can all negatively impact your indoor air.
One way you can improve your indoor air quality is with a CERTIFIED asthma & allergy friendly® air cleaner. Many air cleaners claim to control allergens. But there is no regulation on the terms like "hypoallergenic" so some products make false or exaggerated claims. The asthma & allergy friendly® Certification Program helps people make informed purchases for a healthier home. We test household products, such as air cleaners, against strict standards. If products pass our tests, they earn the asthma & allergy friendly® mark.
Here are some things to keep in mind when shopping for an air cleaner.
Air and Room Capacity
Before selecting an air cleaner, consider the size of the room so the air cleaner you select is powerful enough. A useful way to determine this is by an air cleaner’s CADR rating. CADR, or clean air delivery rate, is the performance metric to indicate the effectiveness of an air cleaner. If you purchase an air cleaner with a CADR rating too low for your room, it will be ineffective. While CADR is a key measurement for selecting an air cleaner, MERV (minimum efficiency reporting value) is important for selecting the right filter. The MERV rating is a measure of the size of particles the filter will remove. HEPA filters are normally rated MERV 13.
PM2.5 vs. PM10
PM stands for particulate matter, and the number that follows it refers to the size of the particulate matter in microns. A micron is one-thousandth of a millimeter. (The period at the end of this sentence is about 400 microns!) The primary sources of these particles are cooking, automobile emissions, dust and fires. Larger inhaled particles are normally captured by the hairs in your nose, but particles of sizes less than PM10 can bypass this defense. The smaller the particle, the deeper it can make its way into your airways, and potentially the more damage it can cause. Particles that are defined as PM10 include dust, pollen and sea salt. Particles defined as PM2.5 are generally particles emitted from the burning of coal, wood, rubber and other materials.
Modes of Filtration
Air cleaners or air purifiers are designed to remove particulates and sometimes odors from the air we breathe. There are several ways they filter the air.
Media-based filter: Filters are generally ranked according to the particle size they trap. Over time, filters need to be replaced as they become clogged. The efficacy of a filter is dependent upon the integrity of the seals. Depending on how effective a filter is, it may be described as a HEPA (high energy particulate air) filter.
Electrostatic filters: As the particles in the air pass through the electrostatic filter, they receive a charge. This allows them to stick to metal plates in the air filter.
Activated carbon filters: These filters are made of porous carbon. As odors and gases pass through the carbon filter, they become trapped in the pores, unable to pass through. The pores may become clogged over time and will then need to be replaced.
Ionizers and ozone generators produce different types of molecules but work in a similar way. They produce ions or ozone which is released from the air cleaner/purifier to be distributed around the room. Allergenic particles normally floating around a room have a neutral or no charge, so when they encounter ions or ozone, they become charged and can stick to surfaces around the home. This removes them from the air. They can then be removed from these surfaces by normal day-to-day cleaning.
Ozone is a gas that is highly reactive. It can be formed naturally or as a result of human activity. If ozone is inhaled, it can travel all the way to the lower respiratory tract where it can damage your lungs. Many electrical devices (including air cleaners) produce ozone as a by-product. This cannot be avoided. CERTIFIED asthma & allergy friendly® air cleaners are tested to ensure that they don’t produce harmful levels (greater than 0.05 parts per million) of ozone.
Ionizers release ions into the environment. Ions can be positively or negatively charged. Their main function in air cleaning is to pass their charge onto neutral air particles. By passing on this charge, it causes the particles in the air to stick to surfaces, removing them from the breathing zone. Research in the area of negative ions supports the safety of these ions. However, there is not as much research performed on positive ions. Anecdotal, unsupported research indicates that positive ions may have a detrimental impact on health. Air cleaners with an ionizing function must produce mostly negative ions to comply with certification.
UV light sources can sometimes be present in room air cleaners and in HVAC systems. UV light requires time to kill microorganisms (bacteria, viruses, fungi), but it doesn’t happen immediately.
Impact of Outdoor Air Pollution
Your indoor air is very much a function of your outdoor air. So if you live in an area with high outdoor air pollution, it transfers to your indoor environment. This will impact how often you need to change your filter and how long you need to run your air cleaner. For example, smoke from wildfires can contain a wide range of particles at very small size – as low as 0.4 micron. Carbon monoxide, a dangerous gas, can also be produced during fires, so you could use an air cleaner with a media-based HEPA filter (to capture particles as low as 0.3 micron) and some type of carbon or zeolite filter to capture any gases that may enter your indoor environment. Due to the high air pollution following fires, filters would need to be changed more regularly and air intake should be set to recirculate rather than using fresh air intake.