If you suffer from respiratory allergies, an air purifier may help you reduce the severity of your symptoms. Many different types of air purifier are available. Learning the basics about air purification can help you make the right choice and allow you to breathe easier.
Filters
Basically, an air purifier consists of a fan that blows air through some mechanism designed to remove contaminants. In most cases, this is a physical filter which blocks dust and other particles, and must be changed regularly to keep the purifier working. The owner's manual will indicate how often the filter must be changed--in most cases somewhere between every three months and every year.
Ratings
There are two commonly used rating systems to describe air filter effectiveness. The Clean Air Delivery Rate (CADR) certification describes how much filtered air a purifier can deliver. As a basic rule of thumb, multiply the square footage of your room by two thirds to determine the CADR rate necessary to keep the air clean. Minimum Efficiency Reporting Value (MERV) is a scale that indicates the filter's ability to remove contaminants, with standard furnace and air conditioner filters rating 1 to 4 and high-efficiency HEPA filters rating as high as 20.
HEPA
High Efficiency Particulate Arrestor (HEPA) filters are among the best air filters available. For a filter to receive HEPA certification, it must trap 99.97 percent of all particles greater than 0.3 microns in size, which covers the vast majority of airborne contaminants. It's important to ensure that any filter you purchase is certified as HEPA and not "HEPA-type"; while a HEPA-type filter may be very effective, only the actual certification will guarantee maximum air purity.
Electrostatic Purifiers
In addition to filter-based purifiers, there are purifiers which use electrostatic technology to clean the air. These units give the particles that pass through them a negative charge, which can then cause them to stick to charged metal plates within the unit. Any particles which make it past these plates will have a tendency to settle out of the air, sticking to walls or other surfaces. These units are generally not as effective as filter-based purifiers, and must be cleaned regularly to keep them in good working order.
Ozone
Another type of air purification system utilizes ozone to clean the air. Ozone is an unstable oxygen molecule that can oxidize particles it comes in contact with, destroying them. Ozone is good for removing biological contaminants from the air, but it can be harmful in high concentrations. If you have small animals or anyone with respiratory conditions in your home, you'll want to avoid this type of air purifier.
