The best air purifiers for allergy and asthma patients contain very fine filtration systems, usually HEPA filters, coupled with additional particulate controls. An internal fan pushes air through the filter to remove particulates before circulating the cleansed air back into the space. Before purchasing an air purifier, measure the area of the space and check the clean air delivery rate (CADR) rating to make sure the unit will run efficiently.
The BlueAir 203 uses an electrostatic polypropylene fibre filter to capture fine particulates that can irritate asthma and allergy patients, yielding a (CADR) of 115 for smoke, dust and pollen. This rate is ideal for rooms up to 154 square feet. Air flows freely through the filter, quickly replenishing the room with a clean allergen-reduced atmosphere ever 12 minutes. Since the filter is large enough for air molecules to easily pass through, the BlueAir 203's fan works less, decreasing the unit's volume. The maximum size of the room in which the unit can effectively cleanse all the air five times per hour is 198 square feet due to the purifier's compact size. As of 2009, the BlueAir 203 was available for £195.
The Airgle 750 is a powerful air purifier with a CADR rating of 450 for smoke and pollen and a CADR rating of 400 for dust. Designed to trap nearly all allergens using 12 stages of filtration, the system boasts four permanent pre-filters, four HEPA filters, two activated carbon filters and two high airflow filters. The pre-filters catch large pollen particles while the HEPA filters remove the majority of smaller particles. The high airflow filters contain an antimicrobial agent to destroy any other living organisms in the air before returning it to the room six times per hour. The Airgle 750 is designed for rooms up to 698 square feet in area, and it was awarded the Highest Clean Air Delivery Rate by the Association of Home Appliance Manufacturers in 2008. As of 2009, the Airgle 750 costs £520.
IQAir Health Pro HEPA Compact
The IQAir Health Pro HEPA Compact air purifier is designed to filter mould spores, pet dander, dust mites and smoke particles from the air. It is not CADR certified, but the system is able to fully clean the air from an area of up to 900 square feet. It is ideal for allergy and asthma sufferers due to its lightweight construction and long-lived filtration system that only needs to be replaced an average of every one to three years. The IQAir Health Pro uses two filters: a pre-filter for large particulates and a very fine HEPA filter for smaller particles. The unit's manufacturer, IQAir, is a partner with the American Lung Association, a non-profit organisation that promotes clean air and smoke-free living for healthier lungs. In 2009, the IQAir Health Pro HEPA Compact air purifier retailed for £487.
Alen T300 HEPA UV Tower
The Alen T300 HEPA UV Tower air purifier is recommended for asthma and allergy sufferers. It has a CADR rating of 142 for smoke, dust and pollen, and its optimal operating area is 225 square feet. The unit uses a HEPA filter to remove allergens and a carbon filter to remove odours. An ozone-free ioniser attracts some small pollutants with static electricity while a built-in UV lamp kills airborne bacteria. The upright design is ideal for tight, narrow spaces such as home offices and long hallways. In 2009, the Alen T300 HEPA UV Tower sold for £195.