We thank Mr Yip Wai Hon for his letter (Why roll back anti-mosquito policy? Sept 27).

Under the National Environment Agency's Code of Practice on Environmental Health, the placement of air-conditioning trays or receptacles beneath or on top of any air-con unit is discouraged, as the accumulation of stagnant water on such trays could result in mosquito breeding.

If water is found to be dripping from outdoor air-con units in HDB blocks, flat owners should check if the air-con has been properly installed and maintained. This includes checking if proper water discharge measures like affixing a pipe into an internal floor trap have been adopted, and engaging a contractor to service the air-con.

Flat owners who still encounter issues with dripping water from their air-con could consider installing an HDB patented air-con tray to collect the condensate.

Designed with a gradient , this tray has been tested to effectively channel the condensation from the air-con into a discharge pipe.

There was no problem of stagnant water or debris. The trays are in use in several homes and effectively solve the dripping problem. Still, these trays have to be checked regularly to ensure that they are functioning properly.

The tray is available for purchase through a vendor and the installation can be carried out by an air-con installer at a cost.

Michelle Ng Chwee Geok (Ms)

Director (Housing Maintenance)

Housing & Development Board

Tony Teo

Director, Environmental Public Health Operation

National Environment Agency