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Beware of the Potential Hazards of Hand Warmers - CHOICE # 411

  • 2011.01.14

Warm pads or hand warmers are popular with consumers in the chilling weather.  However, consumers have to beware of the potential hazards in using them, in particular liquid fuel hand warmers.

Liquid fuel hand warmers are recently promoted in the market.  To operate the hand warmer, the user has to fill it with lighter fluid and ignite at the catalytic burner unit.  According to the supplier's information, heat is generated through evaporation and oxidation of the liquid fuel, but an expert pointed out that the process is actually the combustion of the liquid fuel.  The product claims to be able to maintain warmth to a maximum of 12 hours.

The expert warned of fire hazard that could occur due to leakage when too much lighter fluid is added or the use of inappropriate fuel.  Consumers should not overlook the potential risk of such product just because no naked flame can be seen.  Apart from carbon dioxide, carbon monoxide and a weak smell of fuel could be released during operation.  In a confined area, high concentration of carbon monoxide has adverse effects on human beings and may even cause death.

Temperature is another concern.  In a test conducted by the Consumer Council, the temperature of the body of the product's metal case was found exceeding 70℃ while the top could reach up to 100℃.  The hand warmer should be kept in its external case and wrapper when in use to avoid direct contact with the skin which might cause burns.  

As the relevant regulations now stand, there are apparently loopholes in the monitoring of the safety of these products.  Consumers are therefore advised to figure out how to use the product safely and be aware of its potential hazards before use.  Product suppliers are urged to provide appropriate warning label on the metal case of the liquid fuel hand warmer.  Due to the complicated operation procedures involved in activating the hand warmer, children and elderly people are not advised to use the product on their own.

The USB rechargeable hand warmer is another product new to the market.  It can be charged by connecting to a computer.  However, there has been a complaint that USB hand warmer fell short of its claimed temperature and was ineffective due to its small size.

Disposable warm pads are common hand warmers but consumers should not ignore their potential risk.  According to the information provided by the Hong Kong Poison Information Centre, there were 8 incidents of elderly people ingesting the content of disposable warm pads from 2006 to 2009.  

The warm pads contain a mixture of iron powder, activated charcoal, vermiculite and salt.  Ingestion of the content may cause burn to the oral cavity and esophagus or gastrointestinal disorder.  Since some disposable warm pads are similar in size and appearance to packets of soluble granules for certain drinks, they should be kept properly and out of reach of children or elderly people.

Some consumers may have chosen electrothermal bags for convenience. In 2006, the Council, in collaboration with the Electrical and Mechanical Services Department, examined 28 models of electrode-type electrothermal bags and found that none of them complied with the relevant safety standards.  Consumers are urged not to use this kind of products.

The January issue of CHOICE also offers safety tips for consumers when using other types of thermal pads:

  • Microwavable heating pads - They are heated in microwave ovens and can be used repeatedly.  Leakage of the fluid from the warmed pads could scald users.  Users are advised to check the instructions (e.g. suggested heating time and output power as well as the output power of their own microwave oven) before heating.  
  • Sodium acetate thermal bags - They can be recharged by boiling in water for around 10 to 20 minutes.  To prevent direct contact, users should separate the bags from the bottom of the cooking utensils with towel prior to boiling.  Never put this type of thermal bag into a microwave oven for recharge.
  • Traditional warm water-bag / warm water-flask - Check the bag or the flask for leakage before adding hot water into it. Make sure the container cap can be closed tightly.  It is not advisable to fill the containers with boiling water.  Avoid applying excessive pressure on the bag which could cause water spill.

Consumers are also advised to avoid prolonged direct contact of the warmers with the skin on the same area.  Prolonged close skin contact to warmers may cause burn injury even if they only exceed normal body temperature slightly (such as at 43℃).

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