Thermal burns by definition are simply “heat burns.” This can be potentially confusing because all burns are associated with heat in some way. It’s easiest to think of thermal burns as a base concept of a burn—a burn resulting from any traditional heat source—and to use this concept in order to differentiate between the unique characteristics of other burn types. Thermal burn sub-classifications (contact, flame, flash, and scald) are also useful for providing clarification.
There are two predominant characteristics that determine the severity of any thermal burn. First is the intensity of the heat source. People often think of heat as measured by temperature (Fahrenheit or Celsius). This is an easy-to-use method to get a rough estimation of how much heat a heat source is putting off. For example, water at 212 ºF is going to put off more heat than water at 150 ºF.
The second characteristic is the duration of exposure to the heat source. The heat a person feels while receiving a burn is actually a transfer of energy from the heat source into the person’s body. The amount of energy transferred into body tissue is directly proportional to the amount of time the tissue is exposed to the heat source. The first step in treating any burn is to remove the exposure to the heat source in order to stop this transfer of energy.
Contact burns are injuries caused when a body part comes in contact with a hot object or substance. Because the burns stem from direct contact with a hot object, they are typically relatively small in size, less than 10% of TBSA. Contact burns also have a very low mortality rate; even burns requiring admission to burn centers have a mortality rate of less than 1%.
As with most types of injuries, the risk of complications associated with contact burns increase as the patient gets older. The most common complication is cellulitis, a potentially serious bacterial skin infection which presents as swollen, red area of skin that feels hot and tender. For those cases that do require burn center care, the length of care is generally less than one month indicating that long term effects are rare.
Common Contact Burn Sources
Contact burns account for approximately 9% of all burns requiring admission to burn centers and are particularly common among young children under the age of five. Nearly 70% of these burns are non-work related injuries that occur in the home. This makes logical sense given that children tend to be tactile learners and the variety of hot objects commonly found around a home. As such, contact burns can often be prevented by simple safety precautions, especially if there are young children in the home. Keep children out of rooms with hot appliances, like the kitchen or bathroom, and make sure to keep plenty of protective cooking equipment handy, such as oven mitts.
The next most common locations where contact burns occur are during recreational or sporting activities. Again, simply being mindful of the danger that these activities pose is the most effective safety precaution. Be wary of equipment that has been sitting out in the sun and bear in mind that engines get extremely hot when they’ve been running.
Flame burns result from exposure to open flame. The source of the flame could be anything from a candle to a forest fire. A common serious complication with flame burns is the potential for smoke inhalation. Inhalation injuries in general have common characteristics and complications that are better discussed on their own. A full description of inhalation injuries can be found on the Inhalation Injuries page. Generally speaking, flame burns are one of the more dangerous types of thermal burns. As mentioned, the most intense forms of flame burns are flash burns which are discussed in their own section below.
Flame burns account for approximately 43% of all burns requiring burn center treatment and are most common among men age twenty to fifty. Like contact burns, flame burns are most commonly non-work related injuries that occur in the household. The nature of flame burns leads to a higher need for excision, cutting the dead tissue away, which is necessary in 18% of all cases that require admission to a burn center.
These burns vary greatly in size, but less than 5% of flame burns are greater than 50% of TBSA. Over half of all flame burns are still less than 10% of TBSA. Mortality rates of flame burns are related both to the size of the burn and the age of the victim. Females also have a slightly higher mortality rate than men.
Common Flame Burn Sources
House fires are the highest risk for most people sustaining serious flame burn injuries. The U.S. Fire Administration recommends that every household take the following precautions to avoid flame burns due to house fires:
- Have at least one working smoke detector at all times,
- Avoid electrical fires by using circuits and extension cords appropriately,
- Follow manufacture guidelines and safety precautions on appliance usage,
- Appropriately insulate and maintain all heat sources including space heaters,
- Install home fire safety sprinklers, AND
- Create an escape route from the home in case of a fire.
Work related fires make up the next largest percentage of flame burn sources. The exact nature of these burns varies depending on the field of work, but safety is best assured by being familiar with potential hazard areas. Occupational Safety and Health Administration’s (OSHA) guidelines set a base standard that any workplace should adhere to.
Flash burns are injuries that result from exposure to an extremely intense heat for a brief duration of time. These types of burns typically are the result of explosions where there is a large amount of flammable gas that all ignites at the same time, referred to as gas explosions. They are also caused by brief but intense flashes of electricity when the electrical current does not actually enter the body but puts off a tremendous amount of heat close by (such as a nearby lightening strike).
Since flash burns only expose the victim to heat for a brief period of time, clothing can often protect the body from at least some of the harm. However, if the flash is intense enough it can catch clothing on fire which may lead to other types of burns. If clothing does catch on fire, smother the flames with a heavy duty material or use the childhood teaching of stop, drop, and roll.
Other than workplace accidents, the most common forms of flash burns are in the home. Natural gas is odorless and colorless, but when used in residential homes the chemical mercaptan is added to give the gas the distinctive rotten egg smell. If you smell gas, avoid using electricity and get out of the building immediately. Once outside call emergency assistance, either 911 or the number to your local gas emergency line. Another important protective measure is to contact your utilities department before digging around your home. Take the time to find out where gas lines are to avoid the potential of a devastating explosion.
Scald burns are injuries from a hot liquid or steam. Liquids transfer their heat more rapidly than solids which means that scald burns can cause deeper burns more quickly than most contact burns. That being said, most scald burn injuries still fall in the first or second degree burn category.
Scald burns account for approximately 34% of all burns requiring burn center care and are particularly common among children between one and five. Over 70% of scald burn injuries occur in children under the age of ten. While mortality rates from scald burn injuries are low, it’s estimated that over 100 people each year die from them.
Most scald burn injuries are caused by high-temperature water whether it is directly from the faucet or while used in cooking. The American Burn Association estimates that 100,000 scald burn injuries each year are caused by spilled beverages and food.
Because liquids rapidly transfer their heat, scald burns can occur in just 1 second when water is 155 °F, 15 seconds when water is 133 °F, and 5 minutes when water is 120 °F. A safe temperature for bathing is 100 °F. The American Burn Association recommends the following safety precautions to minimize the risk of scald burns:
- Supervision—the single most important factor in preventing tap water scald burns,
- Keep hot liquids safely away from children,
- Test the temperature of hot food before giving it to children,
- Angle pot handles toward the back of the stove so children cannot access them,
- Test bath water temperature for several seconds, AND
- Change thermostat settings to heat water to no higher than 125 °F.