Implosions Under Negative Pressure
ENVIRONMENT, SAFETY & HEALTH BULLETIN
Assistant Secretary for U. S. Department of Energy
Environment, Safety & Health Washington, D.C. 20585
DOE/EH-0248 Issue No. 92-2 August 1992
IMPLOSIONS UNDER NEGATIVE PRESSURE
Several recent incidents at Department of Energy (DOE) facilities were the
result of implosions (an inwardly directed explosion) in DOE laboratories. Implosions
laboratory facilities may occur when vacuum pumps, or other equipment that creates
negative pressure, are used in conjunction with glass laboratory containers, such as Dewar
flasks, or when such equipment is used in the vicinity of glass windows and viewpoints.
Although the force of an implosion is directed inward, glass fragments may be propelled in
all directions. In addition to the cuts these fragments may inflict, they may imbed in the
flesh and, in the process, inject toxic, corrosive, or irritant products into the body.
Several of the implosion-related incidents that have occurred at DOE, as well as
recommended actions to ensure worker safety, are discussed below. Improper Selection of
Glass Containers Contributes to Incidents When laboratory work requires a procedure
involving a vacuum, the use of round-bottomed flasks is preferable. In two recent
incidents, selecting the wrong container for a procedure that involved a vacuum
contributed to the resulting implosion. In one DOE laboratory, a chemist received
superficial chemical burns to the face when an implosion occurred during the routine
preparation of an acrylic acid compound. At the time of the incident, the chemist was
removing oxygen from a glass flask in which he had been collecting a filtered solution of
water and sodium hydroxide. Shortly after the chemist began the evacuation process, the
bottle imploded, projecting its contents onto his face and clothing. Fortunately, the
chemist was wearing safety glasses and protective clothing, and his burns were only
superficial. During their investigation into the incident, investigators found that when
collecting the water/sodium hydroxide solution, the chemist substituted a 4-liter
Erlenmeyer flask for the 1-liter, vacuum-filter flask called for in the laboratory's
procedures. However, the flask the chemist substituted was structurally incapable of
withstanding the pressure of a vacuum.
In a similar incident at another DOE facility, a worker was evacuating a 6-liter
glass bottle that contained 3 liters of acrylamide in water. About a minute after the
evacuation process began, the bottle imploded, dispersing acrylamide solution throughout
the room. Injury was prevented only because the worker was not directly in the path of the
bottle. In this incident, the worker selected an "aspirator" bottle, which is a
cylindrical, flat-bottomed bottle with a narrow neck and a glass hose fitting near the
bottom. This type of bottle is not designed to withstand a high vacuum. Glass
Windows/Viewports/Panels Implode Windows, glass viewports, and other glass components and
equipment found in a laboratory are also vulnerable to implosion when under negative
pressure. A laboratory worker at one DOE facility, for example, was injured while trying
to locate a vacuum leak. The worker was kneeling across a component being used in an
experiment when the glass viewport of the component imploded, then exploded, and sent
glass fragments in the worker's abdomen. It is believed that there may have been a
structural weakness in the glass and that this weakness, combined with pressure from the
worker's body, caused the implosion. To avoid similar incidents in this laboratory, the
glass viewport in the component was replaced with a plastic one. In a second
implosion-related incident, an undiscovered leak in the glovebox atmosphere sampling line
created an excessive vacuum within the glovebox and resulted in the implosion of the front
glass panel of the glovebox. This incident was finally traced to failure to install an
"oil bubbler" (i.e., a pressure-relief device) designed by the glovebox
manufacturer. The purpose of the oil bubbler is to draw room atmosphere into the glovebox
to relieve excess vacuum or let air escape to relieve excess pressure. Had the device been
installed, the implosion would have been prevented.
Shielding in the Laboratory Enhances Worker Safety
The use of appropriate shielding is essential when working with materials that
may either implode of explode. Adequate shielding is essential to worker safety in such
cases, because it provides a barrier between the worker and glass fragments. One method of
shielding that is effective when the potential for either an implosion or explosion exists
is the use of a laboratory fume hood. Conducting experiments inside the hood with the
vertical sash lowered provides protection from flying glass on all four sides of the
experiment and contains any potentially hazardous or toxic substances should an explosion
or implosion occur. In addition, in a November 1989, Safety Note, "Glass Containers
Shatter During Experiments with Volatile Materials" (DOE/EH-0119), the Office of
Environment, Safety and Health offered recommendations for appropriate shielding of
laboratory personnel whose work requires handling explosive or energetic materials.
The shielding information in this publication, which was taken from the DOE
Explosives Safety Manual, Chapter 11, Section 21 (page II-67), is currently being updated.
For additional information on shielding, refer to the Manual or call Gerald Meyers at
The potential for an implosion that results in injury to laboratory personnel
exists in any DOE facility where vacuum pumps are used in the presence of glass.
Laboratory procedures and practices should be reviewed and revised as necessary to reduce
this potential risk to worker safety.
Maintain equipment in good working order, with all safety systems
Use filament tape on Dewars, cold taps, and thermos bottles to restrain
fragments in case of implosion, unless an oxidizing gas such as oxygen or ozone is being
stored. (Organic wrappings that contain volatile plasticizers or adhesives may ignite when
the flask is used with an oxidizing gas.)
Conduct experiments that have the potential for resulting in an explosion or
implosion inside a laboratory fume hood with the vertical sash closed and the exhaust
system turned on to ensure that glass fragments and/or toxic or hazardous substances are
Replace glass containers with plastic wherever possible. Polycarbonate (Lexan)
is preferable over acrylic (Lucite or Plexiglas) as it is considerably less combustible.
Use only borosilicate glass when flame or heat will be applied to the container.
Ensure that laboratory procedures specifically state the type of container to be
used, and monitor employees to ascertain that they are using the containers described.
Use safety goggles and other appropriate protective equipment, such as face
shields and protective clothing, when conducting laboratory procedures that require the
use of vacuum pumps or other equipment that creates negative pressure.
Provide regular training in basic laboratory safety practices, and stress the
necessity of wearing appropriate protective equipment and clothing.
This Bulletin is one in a series of publications issued by EH to share
occupational safety information throughout the DOE complex. To be added to the
Distribution List or to obtain copies of the publication, call (615)576-3482. For
additional information regarding the publications, call Barbara Bowers, Safety Performance
Indicator Division, Office of Environment, Safety and Health, U.S. Department of Energy,
Washington DC 20585, (301)903-3016.