Understand VOCs methanal
Formaldehyde is a colourless chemical gas with a pungent odour at high concentration.
It is high irritating to the eyes and respiratory tract. Exposure over prolonged periods may lead to hypersensitivity, whereby people may suffer severe deleterious reaction upon subsequent exposure at very low levels.
The International Agency for Research of Cancer classifies is as a human cancer causing substance.
(Sources from: IAQ Centre, EPD, HKSAR)
How does formaldehyde get indoors

Formaldehyde is a common indoor air pollutant. Levels of formaldehyde are usually higher indoors than outdoors because there are many indoor sources of formaldehyde, and the levels become concentrated with poor ventilation.
The predominant emission source of formaldehyde is pressed-wood products made with urea-formaldehyde resins. These resins are used as adhesives in materials such as particle board, medium-density fibreboard, plywood and other pressed-wood products.
Emission of formaldehyde is released more slowly, but the release continues for a long period of time, often over a number of years.
Formaldehyde is also emitted from cigarette smoking and combustion sources such as gas appliances, and kerosene heaters. Formaldehyde may also be found in other interior decorative items such as foam insulation, adhesives, fabrics, carpets and floor coverings, and in paper products and cosmetics.

(Sources from: IAQ Centre, EPD, HKSAR)

How do I know if there is a potential formaldehyde problem

Exposure to high concentrations of formaldehyde for even short period of time can cause temporary burning or itching of eye and nose, sore or burning throat, and headaches. At even higher concentrations, the severity of the irritation increases and can spread from the nasal passages and throat into the lower respiratory tract. You may have a potential formaldehyde problem when there are significant sources of formaldehyde in your premises or you experience definite symptoms of irritation. The following premises are more susceptible to high levels of formaldehyde:

interior room decoration of new pressed-wood walls, furniture, carpeting, floor covering or furnishings; and
with the windows shut or the fresh air intake of air-conditioning/mechanical ventilation systems kept closed most of the time.
  (Sources from: IAQ Centre, EPD, HKSAR)
What are the tips to reduce formaldehyde exposure
  Here are some tips to reduce formaldehyde exposure at your premises:
The most effective approach is to keep major sources of formaldehyde out of your premises. This is best done by avoiding building materials, furnishings, or other products that emit formaldehyde, particularly pressed-wood products made with urea-formaldehyde resins.
Generally speaking, furniture that consists mostly of bare pressed-wood products will emit more formaldehyde than those constructed of pressed-wood products that are covered fully by laminate or a water-repellent liquid finish. A rule of thumb is that is the finish can keep water away from the pressed-wood material, it can also reduce the escape of formaldehyde from the material. Polyurethane varnish, oil-based alkyd resin paint and thick vinyl film are some of the suitable coating materials.
Old furniture and furnishings, especially those constructed of solid wood, usually emit relatively little formaldehyde. You may consider not to replace them by new ones unless absolutely necessary.
New furniture should preferably be aired out for at least several days or weeks before they are admitted indoors. You may consider asking your furniture supplier or distributor to have them aired prior to delivery to your premises.
Pay attention to the formaldehyde content of wooden panels of new furniture. Formaldehyde emission problems can be greatly reduced if the furniture is made from wooden panels with formaldehyde content meeting the European E1 standard or in compliance with the China GB18580-2001 or similar standards.
Increase the ventilation of your premises to reduce the accumulation of formaldehyde. Open windows wide and for as long as possible, and/or open the vents of your air conditioner.
Emissions of formaldehyde increase as humidity and temperature increase. Reducing humidity and temperature on hot and humid days will help reduce formaldehyde levels.
(Sources from: IAQ Centre, EPD, HKSAR)
How can I measure indoor formaldehyde levels
Before deciding if you need any measurement, you should explore the abatement measures mentioned above to reduce the exposure. If you really want to make measurements to determine the level of formaldehyde in your premises, you should seek help from environmental professionals to carry out the sampling, analysis, and interpretation of results.
(Sources from: IAQ Centre, EPD, HKSAR)
  (Please contact us at 6488 9818, we can make measurements to determine the level of formaldehyde and give suggestions.)