When we’re looking at burns, we’re going to be looking at four main factors. The type of burn, the amount of surface burned, the depth of the burn and the location of the burn. 

Before we dive into that, it’s important to understand that burns are just one type of severe alteration in skin integrity. We will also treat patients with massive skin injuries essentially the same. This includes patients with de-gloving injuries, Stevens-Johnsons syndrome, frostbite, TENS (toxic epidermal necrolysis syndrome) and even road rash.

Factor #1: The Type of Burn

Burns can be classified as electrical, radiation, chemical or thermal. 

Electrical burns are caused by exposure to any electrical current, such as sticking a finger in the light socket (don’t do that!), touching a live power line or getting struck by lightning. Severity of the burn depends on the type of circuit, the voltage and amperage of the current, how long the exposure occurred, and the conductivity of the tissue. The damage with electrical burns is due to hyperthermia (excessive heat) as well as coagulation necrosis, so there’s more subdermal damage than with other types of burns.

When looking at the conductivity of the tissue, some are more electrically conductive than others. For example, bone is less conductive than muscles, blood vessels and nerves. 

Children have the highest incidence of electrical burns either due to putting things in light sockets or chewing on cords. And, interestingly, lightning causes 80 deaths per year in the U.S., with the incidence seven times higher among men than women.


Radiation burns occur with exposure to UV light , radiation therapy or X-rays. The most common type of radiation burn is the sunburn, but also occurs frequently in patients undergoing cancer treatment. A key difference between radiation and thermal burns, is that the damage isn’t immediately apparent with radiation burns. In fact, it can take hours, days or even weeks before damage is noticed.


Chemical burns can occur when the skin comes into contact with a strong base or strong acid, or other caustic substances such as oven cleaner or even concrete mix. These are often related to workplace incidents, with eyes being the most commonly affected area. 

It’s important to note that chemicals are not always liquids, but can also be airborne causing damage to the lungs, mouth and nose. Caustic chemicals can cause harm when touched or swallowed, so the damage can be extensive as well as internal. Additionally, chemicals that cause dermal burns can then be absorbed into the body causing systemic toxicity such as hydrofluoric acid which depletes the body of calcium and magnesium.

Not all chemical burns show immediate damage. Some may be delayed up to 48 hours before the full extent of the injury is known.


Thermal burns are those caused by exposure to heat. Most burns requiring medical treatment are due to thermal sources. Of these, the most common causes are flames and scalding liquids. Adults are more likely than children to be affected by flame injury, while children younger than age five are more likely to suffer from scald burns.

Additionally, when we think of thermal burns, we often think external damage, but the damage can be internal as well. Inhaling hot, smoke-filled air can damage the mouth, nose, airway and lungs. 

Individuals most at risk for thermal burns are those with occupational hazards. A 2007 study showed that occupational burns were highest in those working in the accommodations and food services industry, followed next by manufacturing and then construction. 

Factor #2: Burn Size

One of the key components of burn assessment is estimating the TBSA, the total body surface area that is affected by the burn. Essentially, treatment decisions are based on how much skin is injured, though the depth of the injury also comes into play. Two big factors it helps us determine are whether or not to treat (many burns do not require treatment, whereas others are so severe that palliative care is the only compassionate option) and how much fluid the patient will need. We’ll talk more about fluid resuscitation in another lesson.

We estimate TBSA by using a quick assessment tool called The Rule of Nine which divides the body into nine sections (ten if you count the genitals) which each represent either 9% or a multiple of 9%. This assessment will be done in the field, again in the ER and then again after the initial debridement, which will warrant the most accurate assessment.

Looking at the diagram here, you can see how the anatomic sections are divided into nine main sections 

  • Entire head and neck = 9%
  • Chest = 9%
  • Abdomen = 9%
  • Upper back = 9%
  • Lower back = 9%
  • Entire left arm and hand = 9%
  • Entire right arm and hand = 9%
  • Entire right leg and foot = 18%
  • Entire left leg and foot = 18%
  • Genitals = 1%


When using the Rule of Nines to calculate TBSA, you have to take into consideration partial burns. For example, if the entire left arm is 9%, but only the front of the arm is burned, that’s 4.5%. Similarly, if the forearm is burned all the way around, that would be 4.5%. In addition, only partial and full-thickness burns are considered when calculating the TBSA and anything over 20% is considered a severe burn.

Let’s practice!

Using the Rule of Nines takes a little bit of practice, so let’s go through a few scenarios together.  Scroll down below the references for the answers.


Scenario 1: Your patient is burned on his entire right arm and hand, front of left leg, chest, abdomen, and genitals. What is the TBSA that is burned? 


Scenario 2: Your patient is burned on the abdomen, lower back and back of right leg. What is the TBSA? 


Scenario 3: Your patient is burned on the front of both arms and hands, chest and abdomen. What is the TBSA? 


Scenario 4: Your patient is burned on the front of his head/neck, chest and front of left arm. What is the TBSA? 


A great online calculator is https://www.omnicalculator.com/health/parkland-formula

The Rule of Palm

Another way to estimate the size of a burn is the “rule of palm.” Utilizing this method, the palm of the patient (not counting the fingers or the wrist…just the palm) is equal to 1% of their body. 

Factor #3 Burn Depth

Burns are classified by how deeply they penetrate the skin. 

  • First-degree: Superficial burns that affect only the epidermis. There are no blisters, but the skin is red, painful and dry. Ex: mild sunburn
  • Second-degree: Partial thickness burns that extend partially into the dermal layer. The burn is blistered, red, painful and may be swollen. Partial thickness burns greater than 10% TBSA warrant burn center referral. Ex: burns from hot liquids
  • Third-degree: Full thickness burns that extend into the dermis and possibly extend into the subcutaneous tissue. May appear blackened, charred or even white; upon palpation the burned area may feel leathery and firm and does not blanch. Any full-thickness burn warrants burn center referral.
  • Fourth-degree: Full thickness burns that extend into the deeper tissues, affecting muscle and bone. Patients with fourth degree burns will have no pain or feeling in that area due to destruction of nerve endings.


Factor #4 The Burn Location

Another key factor in assessing the severity of a burn is where it is located. Some burns, due to their location, significantly impact patient outcomes. Because burns to the hands, feet, face, perineum and genitalia affect functional areas of the body, they require special therapies and are best treated at a designated burn center.


  • Head, neck and chest: For these burns I want you to be hyper vigilant and watchful for pulmonary complications. The airway could be burned, you could definitely have smoke and soot inhalation as well.
  • Circumferential burns of arms/legs can have a tourniquet-like effect, leading to vascular compromise distal to the injury. 
  • Circumferential burns of the torso can lead to impaired chest wall expansion and severe pulmonary insufficiency.
  • Burns of hands and joints: Patients with these types of burns will usually require intensive PT/OT and can lead to permanent disability.
  • Facial burns: Consider the possibility of corneal abrasions and serious eye injury.
  • Perineal area burns: High risk for infection


Factor #5: Other Considerations

Other factors that will be taken into account when caring for patients with burns include:

  • Age – higher mortality for children under age 2 and adults over age 60 
  • Associated injuries such as smoke inhalation and trauma 
  • Medical conditions such as diabetes, renal impairment, and any cardiac or pulmonary dysfunction


Get this on audio in episode 149 of the Straight A Nursing podcast wherever you get your podcast fix, or stream it right here.


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Black, Joyce M., and Jane Hokanson Hawks. Medical-Surgical Nursing: Clinical Management for Positive Outcomes – Single Volume (Medical Surgical Nursing- 1 Vol (Black/Luckmann)). St. Louis: Saunders, 2009. Print.

Burn and Reconstructive Centers of America. (n.d.). Radiation burns. Burn and Reconstructive Centers of America. https://burncenters.com/burns/burn-services/radiation-burns/

Church, D., Elsayed, S., Reid, O., Winston, B., & Lindsay, R. (2006). Burn wound infections. Clinical Microbiology Reviews19(2), 403–434. https://doi.org/10.1128/CMR.19.2.403-434.2006

Deglin, Judith Hopfer, and April Hazard Vallerand. Davis’s Drug Guide for Nurses, with Resource Kit CD-ROM (Davis’s Drug Guide for Nurses). Philadelphia: F A Davis Co, 2009. Print.

Paradigm. (2013, August 1). Common Types of Burn Injuries and at Risk Occupations. Paradigm. https://www.paradigmcorp.com/insights/common-types-of-burn-injuries-and-at-risk-occupations/

Rice, N. A., & Greene, S. (2019, June 10). Don’t get burned by hydrofluoric acid toxicity. EMresident. http://www.emra.org/emresident/article/hydrofluoric-acid/

Sutherland, B. (2010, March). Care of the Burn Patient. Advanced Med/Surg. Lecture conducted from CSU Sacramento, Sacramento.

Urden, L. D., Stacy, K. M., & Lough, M. E. (2010). Critical Care Nursing: Diagnosis and Management (Sixth). Mosby Elsevier.



Scenario 1: Your patient is burned on his entire right arm and hand, front of left leg, chest, abdomen, and genitals. What is the TBSA that is burned? 37%

  • Entire right arm = 9%
  • Front of left leg = 9%
  • Chest = 9%
  • Abdomen = 9%
  • Genitals = 1%
  • TBSA = 37%


Scenario 2: Your patient is burned on the abdomen, lower back and back of right leg. What is the TBSA? 

  • Abdomen = 9%
  • Lower back = 9%
  • Back of right leg = 9%
  • TBSA = 27%


Scenario 3: Your patient is burned on the front of both arms and hands, chest and abdomen. What is the TBSA?

  • Front of left arm = 4.5%
  • Front of right arm = 4.5%
  • Chest = 9%
  • Abdomen = 9%
  • TBSA = 27%


Scenario 4: Your patient is burned on the front of his head/neck, chest and front of left arm. What is the TBSA? 

  • Front of head/neck = 4.5%
  • Chest = 9%
  • Front of left arm = 4.5%
  • TBSA = 18%


Four key factors in burn assessment - Straight A Nursing Podcast Episode 149