The facts about immobile suspension in a harness & the need for effective rescue.


Harness Hang Syndrome (or more correctly Compression Avascularisation Re-perfusion Syndrome or 'orthostatic intolerance') is of immediate concern to anyone who works at height in any form of harness or work belt assembly. Surprisingly few people are aware even today of the physiology of unconscious suspension and the need for immediate response. All to often the SAR team will go to a site to conduct training only to be told that the response plan (up until then) for a post fall recovery was to "call the fire brigade' or  'grab a ladder' or 'we hadn't really thought about it before...". Does this sound like your workplace?


In the 1980s a string of caving fatalities in the vertical limestone systems of France prompted Dr Maurice Amphoux to question the factors that contributed to these deaths. Informal initial testing on healthy subjects feigning unconsciousness whilst suspended in a parachute harness produced surprising results. The subjects exhibited symptoms such as sweating, nausea, extreme discomfort, numbness in the extremities and most disturbingly some actually lost consciousness. Further testing was undertaken in controlled conditions with subjects wearing heart monitors…

Dr Amphoux came to the conclusion that a distinct physiological condition, previously unknown or misunderstood, was the contributing factor in the deaths of the cavers. He also surmised that this condition was a serious issue to anyone who may be subject to prolonged mobile or even short term immobile suspension. This condition is known as HHS.

The physiology of a person suspended in a harness is a complex matter. The effect of the harness leg straps may be likened to tourniquets above each thigh in certain circumstances (especially dorsal suspension in a fall arrest harness) and this may bring about a lack of venous blood return or compartmentalisation within the legs. The bodies response may take the form of syncope (fainting / unconsciousness), toxin release within the legs and cardiac arrhythmia.


Testing & research by the Health & Safety Executive in the UK, summarized by Paul Seddon into the most complete work on the subject available today (see below), showed that mean onset times for HHS symptoms may be as little as 4 minutes. Correct pre and post rescue management strategies are vital.  


You can download here for free the technical study on HHS conducted by the UK Health & Safety Executive (it is in Abobe .pdf format so you will need at least Adobe Reader to view it). We strongly suggest all worksite safety managers read it.


Download the HSE Investigation into Harness Hang Syndrome here.





HS1 SAFETY Harness &

static line

HS2 Fall Arrest Systems

HS3 Work Positioning

HS4 Work & Rescue at Height




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