To stand out in the market, many new air purifiers come with bells and whistles.
Besides their main function of removing dust particles, manufacturers say that some can also humidify the air to relieve sinus problems or ionise it to remove bacteria and viruses. Others double as fans or mosquito catchers.
The range is so wide that it is enough to give consumers a headache, haze or no haze. But experts say that when shopping for an air purifier, the most important thing to look out for is a high efficiency particulate air (Hepa) filter.
Dr Steve Yang, 44, a respiratory specialist at Raffles Internal Medicine Centre, says: "Only these can filter out the very small particles, those 0.1 to 0.3 microns in size."
The Government's haze microsite (www.haze.gov.sg) says the main air pollutant during bouts of haze in Singapore is particulate matter. Other pollutants include sulphur dioxide, ozone, nitrogen dioxide and carbon monoxide.
Experts say particulate matter ranges in size, but fine particulate matter - with a diameter of less than 2.5 microns - is particularly harmful. A Hepa filter can filter these particles easily.
Consumers can refer to the Government's haze website for a list of portable air cleaners available in the market.
Purifiers are available at major appliance stores such as Best Denki, Courts, Gain City and Harvey Norman. Prices range from $99 to more than $1,000 each.
When asked, experts declined to comment on the effectiveness of individual brands and models.
Associate professor Rajasekhar Balasubramanian, 53, from the National University of Singapore's department of civil and environmental engineering, says: "Little research has been done on the effectiveness of air cleaners.
"A systematic study is needed to evaluate and compare the performance of different portable air- cleaning technologies in terms of their ability to remove a range of indoor air pollutants during the occurrence of smoke haze events."
The Consumers Association of Singapore recommends using an air purifier when there is haze, "especially for those suffering from respiratory diseases, the elderly and the young".
Case executive director Seah Seng Choon, 62, says: "However, if consumers do not have an air purifier, they can close the windows and turn on the air-conditioning to help reduce the amount of haze particles indoors."
Two weeks ago, housewife Inna Angullia, 36, spent almost $1,200 buying two air purifiers with Hepa filters from Courts. She has two children - a son, two, and a three- month-old daughter. Her husband, 26, is a property officer in a town council.
She says: "The haze this time looks like it is going to last much longer than in previous years and now I have two young children."
Before she bought the purifiers for her three-room HDB flat in Tampines, her baby had a flu and cough and was hospitalised for a night earlier this month. Ms Inna also had a sore throat and found it difficult to breathe.
She says: "Thankfully, now it is easier to breathe at home."
Air purifiers
Novita PuriClean NAP 501
Introduced: December 2013
Coverage: 25 sq m
Price: $369
The device has a Hepa filter and a sensor that will diagnose and indicate the current air quality through the display of different colours. It also has an ioniser that can diffuse more than 20 million negative ions to eradicate airborne germs and allergens.
Tefal Intense Pure Air PU4025
Introduced: June this year
Coverage: 35 sq m
Price: $399
The device has four layers of filters, including a Hepa filter. It can trap big pollutants such as dust, human and animal hairs.
It can also dissipate food smells, animal, paint and tobacco odours, and destroy formaldehyde - a chemical emitted by furniture varnish, paint, cleaning products and scented candles - that can cause allergies and respiratory ailments such as asthma.
There is also a larger model - the PU6025 - that covers 80 sq m and sells for $599.
Sharp FP-FM40E-B
Introduced: This month
Coverage: 30 sq m
Price: $459
The device is equipped with three layers of filters, including a Hepa filter.
Apart from cleaning the air, it also doubles as a mosquito catcher. It attracts mosquitoes using its black body and LED UV lights. When mosquitoes rest on the device's narrow air inlet, they are sucked in by the powerful airflow and trapped permanently on a three-layer glue sheet inside.
Dyson Pure Cool
Introduced:April this year
Coverage: A rate of 13 sq m every 25 minutes
Price: $999
Both a fan and an air purifier, this device circulates purified air across the whole room, unlike conventional air purifiers that typically release purified air straight up to the ceiling.
It has a 360-degree Hepa filter that can capture ultra-fine particles as small as 0.1 microns and a layer of activated carbon granules to capture odours and harmful toxins such as paint fumes.
