Q. What all should I learn about air filters?
A. Whenever we discuss about air pollution, we normally think about outdoor air. But there is a lot of attention being paid to indoor air recently, as asthma has spread in epidemic proportions in the last two decades, in the United States – infants and children who utilize a major part of their childhood indoors suffer the most from asthma. Indoor air pollution has been classified by the United States Environmental Protection Agency in 1990 as a top priority public health risk.

Three plans have been advised by the American Lung Association and the EPA for bringing indoor air pollution under control:

1. Managing all the sources of pollution
2. Providing proper ventilation
3. Clearing indoor air of all pollutants.

Here are a number of answers to some common questions that have been asked when anyone wants to know more about cleaning indoor air.

Q. Can I control my asthma by installing air filters in my house?
A. The American Lung Association and the EPA advices us to filter air but more that that they want us to give more priority to reducing anything that causes allergy and also take care of ventilation.  Our allergy problems cannot be solved by air filters although they are useful tools for a healthier life. Research studies don’t have a common consensus on the relief provided by filters to asthma sufferers in a neat and well-aired home. Although you will find a number of allergenic particles present in indoor air, a greater number is present on surfaces of furniture, rugs and countertops. Your topmost priority should be to keep such places totally clean if you want to control the factors that cause your asthma.

Q. Does air filter have any national health standards to judge their performances?
A. No. Although a group of experts have been asked twice by the Food and Drug Administration (FDA) to come up with national standards, there has been no positive outcome of this. The groups felt that they didn’t have sufficient research material on air filtration and its positive effect on actual health, so they didn’t recommend any national standards. 

But yes, when you are shopping for air filters, you do get a number of rating systems that are supposed to judge the performance of the various filters. You should remember that such rating systems are not health related. They have been given by the manufacturers and their organizations. Thus you will not learn anything new in case you are health conscious.

Q. Show me a way to select a good air filter?
A. The FDA doesn’t provide any health-related standard but they do classify many portable air filtration systems as Class II medical devices. No one can get this status in the US without FDA’s approval. The manufacturer gets this approval on proving the following two things: 1). The safety aspect of the device that is indicated by the Underwriters Laboratory (UL) seal, and 2). The device will benefit a user medically. You should check for the UL seal and the FDA's Class II approval statement. If the FDA statement is not present, look for the FDA's medical device listing before you buy the device. You can also ask your doctor for further help.

Q. Do air filters differ in their types?
A. Yes, you will find that there are five types of filters:

Mechanical filters:  The air is forced via special mesh that is used to trap particles. These particles include dust mites, dander and allergens like pollen. Tobacco smoke too can be captured by such a filter.

Electronic filters: Electrostatic filters are the best performing ones from the lot. Electrical pulses are used to draw and collect allergens and irritants. The particles are absorbed inside the system in case the filter has collecting plates. If not, the particles stick to the room surfaces and need to be cleared away.

Hybrid filters: Such filters use the fundamentals of the electrostatic and mechanical filters.

Gas phase filters: These are useful in removing any kind of smell and also remove cooking gas and other gases that are given off by paint or building materials and perfume. But allergenic substances cannot be removed by them.

Ozone generators: Such kinds of filters do clean the air but they have not been recommended by the EPA and the American Lung Association as ozone will harm the lungs. Asthma sufferers are advised to stay indoors whenever there is a rise in the ozone concentration outside. Thus it would be foolish to generate ozone in the house.

Q. Are filters actually useful in “changing the air” in a room?
A. Of course yes, you should buy an air filter system that recirculates 8 or 10 room volumes per hour. You are not guaranteed of total clean air but such systems provide cleaner air than the other systems.

Always ask about the filter’s efficiency. A good system will be able to remove over 90 percent of the particles that are larger than 0.3 microns in diameter. Since a majority of the allergens found indoor are larger than this in diameter, the system will easily be able to tackle all such allergens.

Q. Can I get any type of filter that will turn useful for my asthma?
A. Yes. You should choose the high-efficiency particulate air (or HEPA) filter. Please note that it is not a brand name but just a type of filter. This is the best type of filter suitable for your asthma. It was invented during the World War II so that radioactive particles could be prevented from escaping from laboratories. If a device can capture a minimum of 90 percent of particles that are 0.3 microns or more in diameter, then it qualifies to be “genuine HEPA" filter.

You need to be on your guard, as many filters claim to be HEPAs, but perform at half the potential of a genuine HEPA. Always go for a system that is able to perform to the “true HEPA” filtration standards. This will help you to get rid of most of the allergens in your home.

Q. Are these HEPA filters difficult to handle and expensive to buy?
A. No. filters are known to improve as time passes by. This is because the particles that are trapped earlier will block spaces that would have allowed later particles to escape. But they do get blocked over a long period of time and the cost of operation definitely increases. You can easily replace the mesh every year so that its performance gets enhanced.

You should clarify all your doubts about the cost, difficulty and the operating life of filters from the salesperson. This will help you to avoid any kind of unpleasant surprises later on.

Q. Is there anything else that needs to be considered by me before I buy an air filtration system?
A. It’s possible to build filters in the air handling systems, if your home has ducts that have been used by heating or air cooling systems. The air will pass through the filters with great force. You can not only eliminate a space-consuming appliance but also remove unwanted sound from your home. But you might have to spend more on the filter and take more effort to handle them – you would also have to change them more often. You should take your doctor’s and heating service’s advice on such a kind of option.   

Questions that need to be asked by you before you purchase an air filter

1. What are the types of substances that can be removed by the cleaner from the indoor air in my home?
2. What are the substances that cannot be removed by the cleaner?
3. How does the efficiency of the cleaner rate when compared to the “true HEPA” standard?
4. Can the unit clean the room’s air when it is the size of my bedroom, that too after every four-six minutes?
5. Can you tell me the clean air delivery rate (CADR) of the device?
6. Is it difficult to change the filter? (Ask for a demonstration.) What is the time duration for changing it?
7. What is the cost of the filters?
8. Are they easily available throughout the whole year?
9. Does the unit make a lot of noise?
10. Will it be sufficiently quiet when I need to sleep? (Check this by turning it on and trying it out even if you are in a noisy place.)