This undated photo shows the Centre for Health Protection of the Department of Health, Hong Kong. (PHOTO / HKSAR GOVERNMENT)

Hong Kong’s health authorities on Friday urged the public to take precautions amid a recent rise in incidents of carbon monoxide poisoning while taking showers.

In a statement, the Centre for Health Protection said it had received a report of an additional poisoning case, where a 59-year-old man was found unconscious while having shower at his home on Tuesday. He was in stable condition after being sent to Pok Oi Hospital and was later transferred to Pamela Youde Nethersole Eastern Hospital for treatment.

This is the third poisoning case in the city in a month. The other cases happened on Jan 18 and Jan 29, as the two residents concerned had used unapproved and worn-out gas water heaters respectively, according to local media reports.

A site investigation into the latest incident by the Electrical and Mechanical Services Department indicated that the gas water heater was of a flueless type and should not be used in bathrooms.

The authorities reminded members of the public of using gas water heaters, which is approved by the EMSD and bears a "GU" mark, in a well-ventilated area. All installations, replacements or repair work on gas water heaters must be carried out by a registered gas installer employed by a registered gas contractor

The model concerned had not been approved by the EMSD and did not bear a "GU" mark, the probe showed.

It is preliminarily suspected that the exhaust flue gas generated by the gas water heater without flue was discharged into the bathroom, coupled with poor ventilation, carbon monoxide accumulated due to insufficient oxygen for combustion and thus led to the carbon monoxide poisoning.

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The EMSD had seized the heater for further investigation and would consider initiating prosecution against the person concerned if the Gas Safety Ordinance was found to be violated, according to the statement.

Carbon monoxide is a colorless, odorless and tasteless gas which is a by-product from incomplete combustion of any fuel which contains carbon. Exposure to a low concentration of carbon monoxide can lead to dizziness, a headache, tiredness and nausea, while exposure to a high concentration can lead to impaired vision, disturbed co-ordination, unconsciousness, brain damage or even death, according to the statement.

The EMSD said a large amount of carbon monoxide may be built up within a short time when a flueless gas water heater is used in a room with inadequate ventilation.

The department reiterated that flueless gas water heaters were not allowed to be installed in a bathroom according to the Gas Safety Ordinance.

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The authorities reminded members of the public of using gas water heaters, which is approved by the EMSD and bears a "GU" mark, in a well-ventilated area. All installations, replacements or repair work on gas water heaters must be carried out by a registered gas installer employed by a registered gas contractor.