There appears to be no end in sight to Hong Kong's pollution woes. On most days, the air is filled with smog.
The city's filthy air has resulted in an increasing demand for home air purifiers.
Teresa Lam, from IQ Air, has seen a 30 per cent growth in demand for air purifiers over the past 12 months.
'Air purifiers are becoming more popular because people are willing to spend money on their health,' Lam explains. 'They want a healthier body and living environment.'
However, Lam warns there are no regulations on the efficiency of air cleaners.
'Anyone can set up a company to manufacture air purifiers and make claims about them, but they don't have to prove or back-up these claims.'
She adds that some can be harmful and produce ozone, especially products such as ionisers, oxygen generators or ultraviolet light systems.
When shopping for an air purifier, Lam says it is important that you first understand the ambient air quality of your home.
'The consumer must know what pollutants are in their home before making a purchase,' she says.
'The filter must pass international standards and you must know there has been an improvement in air quality - the only way to do this is to measure the efficiency with a particle scanner.'
Lam says one customer, a doctor, bought a scanner to measure particles per litre of air when he travels.
'In Canada, he found outdoor air was below 4,000 particles and indoors it was 1,000, but in Hong Kong it measures around 100,000 and sometimes more than 200,000 in winter.'
The Swiss-made IQ Air is the only household-use air cleaner that passes the world's most stringent high efficiency particulate air filter test - the European standard EN 1822. This guarantees minimum particle removal efficiency of 99.97 per cent for all particles larger than 0.3 microns.
The purifier can filter out airborne pathogens, including allergenic, toxigenic and suspected respiratory and non-respiratory pathogens.
Some of these include bacteria, viruses and fungi.
Apart from residential and commercial premises, the systems are also used in the medical field, having been approved by the United States Food and Drug Administration as a Class II medical device.
All Hong Kong public and private hospitals use IQ Air in operating theatres, intensive care units and waiting rooms. Since 2003, it has been a consultant to the Department of Health and Hospital Authority.
Because of their size, IQ Air units generally sit on the floor. However, they can be mounted on the ceiling or wall and connected to the air-conditioning system so that the air is ducted.
Lam says that some of Hong Kong's major developers are incorporating air purifier systems into their properties.