The risk of contact burns from domestic heating appliances

Figures collected by the French Institut de Veille Sanitaire record domestic accidents leading to hospital admission across 12 hospitals. France has more than 600 of them.

Those studies show that between 2004 and 2010, 389 burns were recorded following contact with radiators, electric heaters, gas or paraffin heaters and wood stoves.

The figures in that report would therefore have to be multiplied by 50, or more, to cover the country as a whole.

Here is how the heating systems responsible for serious burns rank:

1. wood stoves: 30%
2. paraffin or gas heaters: 21%
3. electric heaters: 20%
4. other heaters: 17%
5. fireplace inserts: 12%

The same figures show that two thirds of the people burned were children under 5, and that the hand is involved in 75% of cases. Typically these are very young children learning to walk, setting off to explore what is around them with both hands held out in front.

Contact with hot surfaces, radiators or the walls of a fireplace insert, is the third and sometimes the second cause of thermal burns in children, after hot liquids and flames.

• 48% of burns are on the hands
• 60% of cases are second degree burns.

Article 21 of the French order of 4 June 1982 on premises open to the public states that the heating in nursery school rooms must not be directly accessible if its surface temperature is above 60 °C in normal operation.

Standard NF EN ISO 13732-1 of December 2008, on methods for assessing the human response to contact with surfaces, sets maximum contact temperatures for hot surfaces. From those, together with the exposure time, the burn thresholds follow.

The surface temperature of some heating appliances stays very high, and some sellers are happy to talk about a reflex temperature to explain that there is no risk of a burn.

In other words: you put your hand on it, you take it straight off again, and you are not burned.

The burn threshold for a healthy adult is 51 °C for a contact time of 1 minute with a surface of bare or coated metal. It is 56 °C for a surface of ceramic, glass or stone.

The threshold falls to 48 °C, whatever the material touched, for a contact time of 10 minutes.

For very young children under 24 months, the freeze time, meaning the state of shock in which the child stays put, hands stuck to the appliance for several seconds, screaming, without the reflex to pull away, can be put at around 15 seconds.
The burn is then made worse by the absence of an immediate reflex in the child, who stays frozen for several seconds before reacting, where the reaction time of an adult is of the order of 0.4 to 1 second.

What follows from it:

• from 44 °C, a second degree burn appears after an exposure of six hours or more;
• the pain threshold lies between 47.5 °C and 48.5 °C depending on the person. Someone can therefore sustain a second degree burn before feeling any pain at all;
• between 44 and 51 °C, the extent of cell damage doubles with every degree;
• at 49 °C, a second degree burn appears after 10 minutes of exposure;
• at 50 °C, the same damage takes 5 minutes;
• at 60 °C, 4 to 5 seconds are enough to cause a second degree burn;
• at 70 °C, that time is down to 1 second.

Only young adults in good health, whose reflex time is between 0.4 and 1 second, might avoid a serious burn on accidental contact with a metal surface or a liquid at 70 °C.

For children, whose skin is far thinner than an adult's, the second degree burn occurs four times faster than in an adult.

Put your hand on an object made of steel at a given temperature and the cell damage will be greater, for the same exposure time, than after touching an object of the same shape made of an insulating material such as plastic, wood or plaster.

At the moment of contact a thermal equilibrium forms, between the heat absorbed by the skin and the heat supplied by the object.

If the object is steel, an excellent thermal conductor with a great deal of thermal inertia, the contact temperature will barely fall while contact lasts, and the burn to the skin will be particularly deep.

The equilibrium temperature between a steel object at 100 °C and the hand is 98 °C, and it stays there for several seconds. The same holds for a steel object whose outer coating is metallic, chrome plated steel for example, and for water.

An insulating object, by contrast, cannot supply as much heat as steel even at a high temperature, and the contact temperature with the skin falls quickly. The resulting burn is therefore shallower.

That is why, in the table of limit temperatures in standard NF EN 60335-1, it is accepted that glass or ceramic parts may run hotter than steel ones.

Some heating appliances have another function as well: radiators with a decorative glass surface, and also heated mirrors.

The risk of a burn rises sharply when the appearance of the appliance hides what it is actually for, as the reflective surface of a mirror does.

A very young child exploring the room will be drawn to this strange object that gives back their own image. The surface temperature must under no circumstances burn that child, even where a hand is held against it.

For heating manufacturers: protecting children and vulnerable people has to come first.

• Some propose moving the appliance out of reach.
• Others are asking for the contact temperature to be brought down.

For those designing buildings and homes: work with forms of heating built around comfort.

• emitter temperatures as low as possible
• large exchange surfaces.
• better insulation of the building envelope.

Comfort is proportional to the size of the emitter and to how the energy it produces is spread through the room.

Ceilingo offers solutions that are simple and remarkably effective.

• bringing the surface temperature down on these heating systems, which run between 20 and 50 °C
  
• increasing the heat exchange surface with the room, using large heated mirrors and radiant walls and ceilings covering 100% of the treated surface
• keeping outside disturbances out, stray draughts and heat arriving from elsewhere such as sunlight or activity in the room, by making the building airtight.
• pairing effective insulation with the heating element, so its heat goes where it is wanted, and with the room around it, so the temperature of the heated rooms holds.