What could be hazardous about a helium-filled party balloon, you ask? After all, balloons are supposed to be fun, right? The answer may surprise you.
Most people simply do not have the information available to help them understand hazards associated with inhaling helium. Several years ago, I was asked to investigate the death of a teenager who died while inhaling helium from a balloon-filling system. During this investigation, I discovered the true nature of these severe—and potentially fatal— hazards. The discussion here is intended to help readers make informed decisions that will prevent future loss of life.
A little-known aspect of inhaling helium is how quickly you may lose consciousness due to asphyxia (oxygen deprivation). During the exchange of gases in the normal breathing process, the blood stream absorbs oxygen from air in the lungs, while carbon dioxide passes from the blood to the air. When you hold your breath, the exchange of gases slows, as "stale" air in the lungs is no longer replaced by "fresh" air.
This process does not stop instantly, however. Some time will pass before you start to experience serious physical distress. For example, you would likely have time to pick up and put down an object, walk across a room, or find a chair and sit down before feeling compelled to breathe again.
However, when the lungs are filled with helium, a different process takes over. Oxygen is actually removed from the blood stream during the exchange of gases. Depending on how completely oxygen is replaced by helium, you may lose consciousness quickly and without warning—you may literally pass out while still standing. The usual result is an uncontrolled fall that can cause serious injury, even if normal breathing resumes.
Helium balloon-filling systems have become popular in recent years, and are frequently found in supermarkets, party supply stores, and variety stores. The "commercial" type system is generally operated by a store employee rather than by a customer. Sometimes the system is loaned or leased to the customer—a practice that led to the fatality mentioned earlier. A typical commercial system consists of a helium cylinder, shut-off valve, pressure flow regulator, and tilt valve with balloon adapter.
Such a system is designed to fill balloons rapidly. Typically, it delivers a maximum helium gas flow rate of approximately five cubic feet per minute (cfm). Maximum flow rate is determined by the pressure/flow regulator and cylinder pressure—normally several hundred pounds per square inch (psi).
Attempting to inhale helium from a commercial helium balloon filling system poses a greater hazard than does inhaling helium from a balloon. Beyond the risk of passing out, the potential for fatal injury is present. Unfortunately, several young people have been killed while inhaling helium from such a system.
How can a healthy young person be killed by a seemingly harmless substance, you ask? Postmortem examinations of victims explain what occurs, while engineering analysis explains how.
Chemical reaction does not cause fatal injuries. Rather, the pressure of gas inside the lungs is the agent that can kill instantly. Autopsies show that the alveoli (air sacs) in the lungs have been ruptured. Death follows immediately, as the victims literally drown in their own blood. Under such circumstances, cardiopulmonary resuscitation is of no avail.
Gas flow rate of 5 cfm is equivalent to 2.36 liters per second. Although individual lung capacity varies, a reasonable estimate for total lung capacity in an adult female is 4.5 liters. This capacity is used in the calculations that follow.
According to human physiology references, prolonged exposure to a difference of 30 millimeters (mm) of mercury between intrapulmonary pressure and surrounding body pressure can be fatal. If pressure is increased to 80 to 100 mm, immediate fatality is expected . A pressure of 80 to 100 mm of mercury is equivalent to 1.5 to 1.9 psi. For calculation purposes, a mid-range value of 1.7 psi (above atmospheric pressure) is used as the critical value. Furthermore, assume a rigid container with a volume of gas that must be added in order to increase pressure by 1.7 psi.
Calculations show that additional volume required is .52 liters. The minimum length of time required to add this amount (thereby increasing pressure by 1.7 psi) from a balloon-filling system is determined by dividing additional volume (.52 liters) by maximum flow rate (2.36 liters per second). The result is 0.22 seconds.
Since lungs are not a rigid container, actual time to reach 1.7 psi may be slightly longer than 0.22 seconds. However, calculations clearly show that, given the flow rate and pressure available from a helium balloon-filling system, human lungs can be fatally overpressured in a fraction of a second. Victims simply do not have time to react.
Henry G. Wickes Jr., P.E., CSP, is a consultant with and professional associate of Madeley Safety Engineers in Bryan, Tex. 979-693-2041.
This article is excerpted from the December, 1996, issue of Professional Safety magazine with permission of the publisher and the author.
Article provided by the Compressed Gas Association, Inc.