With the amount of allergens in the air, we've got our HEPA air purifiers operating both at home and at work. Air quality is expected to remain "unhealthy" throughout the week according to the government's Air Quality Index, so it's recommended you stay indoors, since the tiny particles can lodge deep into the lungs, causing serious irritation, mucous build-up and breathing problems. If you or someone in your household has health problems or is environmentally sensitive, now might be a good time to research air purification systems. You can also operate your air conditioners, but be sure to operate it with the fresh air intake closed, perhaps investing in a 3M Filtrete Ultra Allergen Filter, an AC/furnace filter that will block out 90% of dust, smoke and smog particles. Below are four of the recommended choices from ConsumerSearch (plus our own recommendation from personal use)... IQAir HealthPro ($695.00): rated the best air purifier overall, and it's expensive price reflects its serious nature. Hong Kong Hospital Authority use these during the SARS outbreak, so you know these machines mean business. The industrial shaped machine can scrub a 1,000 sq. ft. room and uses a HyperHEPA filter, and comes with a five-year warranty. Alen A350($399): this smaller, slimmer wall mountable unit purifies air up to 400 sq. ft., is Energy Star compliant and come with an industry best life time warranty program. A true HEPA filter and a carbon filter removes particles and odours. Whirlpool Whispure AP51030S($299): for rooms 510 square feet or less in size with a 330 Clean Air Delivery Rate (CADR is the amount of clean air measured in cube feet per minute that an air cleaner delivers). Note that replacement filters for this unit are on the pricier side and the unit only comes with a one year warranty. Honeywell Enviracaire 50250($182.25): this compact unit is rated at 250 CADR, and can serve rooms of 374 sq. ft. or less. We personally use and like the Honeywell HFD-130 Germicidal Tower . The $160 unit just costs $5/month to operate on its highest setting, and works best in smaller rooms. We like the 12-hour programmable timer IFD ((intense field dielectric) filter indicator light reminds us when to give the filters a vacuum and wash (there's no filter to replace; you just need to water rinse the filter 4 times per year).