Air Bags and the Skin

Monica Corazza, MD; Silvana Trincone, MD; Maria Rosaria Zampino, MD; Annarosa Virgili, MD

In This Article

Abstract and Introduction

Air bags, fitted in the majority of new automobiles, are safety devices activated when a sudden deceleration causes the ignition of a propellant cartridge containing sodium azide. The bag is inflated by nitrogen liberated during the combustion. Deployment releases various high-temperature gases, including nitrogen and carbon dioxide, and produces sodium hydroxide, a highly irritant alkaline substance. In about 7%-8% of cases, air bags cause dermatologic injuries such as traumatic lesions, irritant dermatitis, and chemical and thermal burns. Nondermatologic lesions, such as ocular damage (alkali keratitis, corneal abrasions), ear lesions, bone fractures, and contusive damage can also be caused by air bag deployment.

Air bags are nylon-and-rubber devices installed in automobiles. In the case of a road accident, the air bags, usually positioned frontally and laterally in the automobile, quickly inflate to minimize injury to the driver and passengers. The devices are activated by rapid deceleration; therefore, even in the case of low-impact collisions, if deceleration is sufficient to set in motion a network of crush sensors, the airbag mechanism may unexpectedly activate.

The sodium azide cartridge in an air bag is activated by a firing signal, at which point nitrogen, carbon dioxide, and other gases are released. The gases inflate a rubber-lined nylon bag in about 30-40 milliseconds and are released through exhaust ports to allow deflation of the bag within 2 seconds. Numerous metallic oxides are produced during combustion and these substances create a fine, alkaline dispersion inside the car. Sodium hydroxide, a highly alkaline substance found in the aerosol is considered the principal cause of chemical burns.

Sodium azide is a highly reactive substance that may chemically react with water, leading to the production of toxic and explosive products. Being an inflammable gas, it may also cause thermal burns after ignition due to sparks produced by electrical devices or high temperatures. Talcum powder may also be present in air bags because it is sometimes used in packaging the devices.

Even though air bags are considered safe, lifesaving devices, their deployment may cause injury. Major damage such as bone fractures (e.g., to the sternum, ribs, and clavicles) and cervical spine contusions have been reported in children and elderly persons affected by osteoporosis[1,2,3] and can be fatal. The release of irritant gases and particulates during deployment can lead to or exacerbate respiratory problems, especially in asthmatic patients.[4]

About 7%-8% of all injuries caused by air bag deployment are cutaneous lesions. With widespread use of this safety device, new, unexpected cutaneous and traumatic injuries have increasingly been reported. Reviewing the pertinent literature and on the basis of our own experience, we believe a review of the various skin lesions caused by air bags is necessary.