Explosions may occur if dry ice is placed in airtight transport containers

British Medical Journal, Feb 17, 2001 by Sally Sharp, David Cummins, Stephen Halloran, Mandy Donaldson, Lynn Turnbull

EDITOR--Since January 1999 all infectious pathology specimens sent by post have had to be packaged according to United Nations approved packing instruction 602.[1 2] This states that the primary specimen receptacle must be placed in an airtight secondary container (figure), which in turn must be placed in an outer, labelled shipping package. The postal service does not require packing instruction 602 to be applied to specimens considered non-infectious, but many laboratories apply it to all specimens sent by post, and some to specimens sent by non-postal courier.

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Pathology specimens transported from one laboratory to another often need to be kept frozen during transit. One method of achieving this is to pack them in dry ice (solid carbon dioxide). We report on four cases in which explosions occurred after dry ice was placed in containers that complied with packing instruction 602.

The first explosion occurred when a laboratory assistant attempted to unscrew the cap of a container into which she had placed dry ice a few moments earlier. She developed massive bruising of her thigh (figure). The second explosion, which happened on a busy section of motorway, ripped apart a motorcycle pannier, with loss of the specimen. The other two explosions occurred after pathology staff received a transport container that was visibly misshapen. One of these explosions blew a hole in the laboratory ceiling and scattered debris over 30 [m.sup.2].

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Dry ice explosions have received surprisingly little attention in the medical literature.[3] When warmed to 20 [degrees] C solid carbon dioxide exerts a huge vapour pressure (28.7 Pa),[4] yet the safety data sheet of at least one manufacturer[4] and the Health and Safety Executive's website (www.open.gov.uk/hse/ hsehome.htm) contain no reference to the explosion hazard. When we contacted product specialists from several companies that market transport containers none was aware of the risk.

We recommend the following:

* All manufacturers of dry ice should refer to the explosion hazard on their safety data sheets

* All airtight transport containers should display a hazard warning

* The Health and Safety Executive should provide advice as to what action laboratory staff should take if they receive airtight containers that might contain dry ice.

We also recommend that laboratory staff receive instruction about the safe dispatch of pathology specimens. Unfortunately, given the shortage of biomedical scientists and the fact that NHS ancillary workers are frequently asked to perform duties for which they have not been adequately trained,[5] dry ice is likely to continue to pose a serious threat to the safe transportation of pathology specimens.

Sally Sharp chief biomedical scientist S.Sharp@rbh.nthames.nhs.uk

David Cummins consultant haematologist Department of Haematology, Harefield Hospital, Royal Brompton and Harefield NHS Trust, Harefield, Middlesex UB9 6JH

Stephen Halloran consultant chemical pathologist Department of Clinical Biochemistry, Royal Surrey County Hospital, Guildford, Surrey GU2 5XX

Mandy Donaldson principal clinical scientist Department of Clinical Chemistry, Hammersmith Hospital, London W12 0HS

Lynn Turnbull quality assurance manager Department of Clinical Biochemistry and Immunology, Leeds General Infirmary, Leeds LS1 3EX

[1] United Nations. Recommendations on the transport of dangerous goods. New York, NY: UN, 1999. (Document ST/SG/AC;10/1/Rev 9.)

[2] International Air Transport Association. Dangerous goods regulations. 40th ed. Geneva: IATA, 1999,

[3] Krajden M, Grigoriew A, Khan M. Potential danger of placing dry ice into a commercial plastic screwcap biohazard safety shipping container. Canada Commun Dis Rep 1993;19:91.

[4] BOC Gases. Carbon dioxide (solid) safety data sheet. Manchester: BOC, 1999.

[5] Institute of Biomedical Science. Recruitment and retention: final results of survey. Biomedical Scientist 2000;44:211-5.

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