Testing conducted by the Consumer Council on 18 models of gas stoves found that the calculated carbon monoxide content of flue gas in 3 models, while in use, exceeded the maximum limit stipulated under the Domestic Gas Appliances Basic Safety Assessment formulated by the Electrical and Mechanical Services Department (EMSD). Moreover, except for 1 model powered by town gas, the calculated maximum heat input of all other models fell short of the manufacturers' specifications. Consumers may make incorrect evaluations of the maximum heating power of these appliances.
Of the 18 models of double-burner gas stoves tested by the Council, half were powered by town gas and half by liquefied petroleum gas (LPG). Each group included 6 models of the built-in type and 3 of the table-top type respectively. Prices for town gas models ranged between $1,480 and $6,580 and prices for LPG models ranged between $1,630 and $4,280. Although prices of some models already cover basic installation, installation fees charged for different brands and by different retailers may cover different scope of work. Consumers should ask the retailer for details about each item before making a purchase.
Test items included safety, heat input of burners, thermal efficiency and ease of use. Safety tests cover all the test items specified under EMSD's Basic Safety Assessment. Those items encompassed combustion test, gas circuit soundness test, surface temperature, flame stability and operation of flame failure device. The results showed that 3 models failed to pass the combustion test, while the remaining 15 models passed all test items.
The Basic Safety Assessment specifies that the calculated carbon monoxide content of flue gas of each burner under the combustion test shall not exceed 0.14% while in use, but the calculated value based on test results of 2 built-in models and 1 table-top model powered by town gas, exceeded the limit by 1.4 to 1.6 times. The calculated content, however, does not equal to the flue gas content of the air in the kitchen when using a gas stove. The test results were referred to the EMSD which expressed it had followed up immediately and contacted the suppliers, and that the appliances pose no safety issues, if they are used in normal circumstances. Consumers should make sure that there is adequate ventilation in the room while using a gas cooking stove, to reduce the risk of carbon monoxide accumulation.
In addition, some consumers have the perception that food cooked with fuel gas is savourier because of the high heat. These consumers prefer models with higher heating power. Consumers may make reference to the heat input level claimed for gas stoves, to identify appliances that meet their requirements. Results of the testing, however, revealed that only 1 table-top model powered by town gas had heat input slightly above their claimed specifications on both burners (i.e. higher by 1.1% and 0.1% respectively), at the maximum flame setting. Among the other 17 double-burner models, the maximum heat input of at least one of the burners fell short of manufacturers' specifications, with discrepancies ranged from 0.1% to 9.7%. The discrepancies of 3 models powered by LPG were greater, with one burner's calculated level falling short of specifications by 8.5% to 9.7%. The discrepancies between test results and the manufacturers' claims for respective models do fall within the tolerance level set out in the Basic Safety Assessment (10%). Nevertheless, the Council notified EMSD of the findings.
Moreover, the test found that the difference of calculated heat input between the left and right burners of some models was relatively large. The heat input difference between the two burners of 1 table-top model powered by LPG was 4.9% and the difference between the two burners of 1 other table-top model powered by town gas was 4.1%.
In addition to considerations of safety and gas consumption, many consumers opt for gas stoves that are more energy efficient. These stoves are environmentally friendly and can save energy costs. The tests discovered that for town gas models, the burner having the best thermal efficiency performance could save 22% of energy consumption when compared with the burner of the model having the lowest thermal efficiency performance. As for LPG models, the burner with the best thermal efficiency performance could save 18% of energy consumption when compared with the burner having the lowest thermal efficiency performance.
Gas stoves are covered under EMSD's Voluntary Energy Efficiency Labelling Scheme but only 12 of the 18 tested models participated in that scheme. The Council suggests EMSD to explore placing gas stoves under the Mandatory Energy Efficiency Labelling Scheme, with the "grading-type" energy labels in place of "recognition-type" energy labels, to facilitate consumers to choose energy efficient appliances.
Consumers should purchase gas stoves bearing the GU mark. After purchasing a new appliance, consumers are advised to read the user manual carefully and be mindful of the following:
- Do not place any item not supplied by the original gas appliance manufacturer, e.g. product with energy saving claim, between the gas appliance and the cooking ware so as to avoid abnormal combustion which may cause an accident;
- Do not put inflammable items (e.g. newspapers, pesticides, aerosol cans and cigarette lighters) near the cooking appliance;
- If the burner does not ignite after ignition, do not reignite soon so as to prevent fuel gas from accumulating for causing fire or even explosion;
- Clean the burner cap and the trivet often so as to keep the burner holes unblocked; if something boils over, clean the burner as soon as possible;
- The installation, replacement and repair of gas appliances must be carried out by registered gas installers employed by registered gas contractors. Arrange for a registered gas contractor to conduct safety checks on all gas installations at least once every 18 months;
- If a gas appliance functions abnormally, stop using it immediately and inform the supplier or registered gas contractor to conduct inspections or repairs;
- If gas leakage is detected, turn off the main gas supply after assuring personal safety and call your gas supply company to send emergency personnel to deal with the gas leak;
- Regularly check whether the flexible gas tubing is damaged, expired or the gas tubing connection joint is loose. If a problem is found, arrange for a registered gas contractor to replace or repair the tubing at once;
- Make sure that there is adequate ventilation in the kitchen while using a gas cooking stove such as open the kitchen windows, turn on cooker hoods or exhaust fans, but care should be taken to keep the flame out of direct wind.
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