Survey on wash-off efficiency of overhead emergency safety showers

Emergency safety showers fed with water have proven to be useful for fire extinction in case persons have caught fire and for the removal of contaminations with hazardous substances. Both in laboratories and in many production sites these emergency showers are an established measure

The focus of all protective measures is on the prevention of fires and of the contamination of persons. As a primary measure, wearing of appropriate clothing and personal protective equipment reduces the hazards considerably. In cases where these measures are insufficient, the use of emergency safety showers as a secondary means of protection is indispensable. While contaminations of the eyes will be removed with eye-wash units, emergency safety showers will be used if the human skin has been contaminated or if the clothes have caught fire.

While the fire extinction properties of emergency safety showers for persons who have caught fire have been thoroughly investigated, the decontamination properties of these showers have not been well understood. The lack of knowledge concerns in particular the effects of the rate of water flowing through the shower head and of the spray pattern on the decontamination efficiency. Preliminary tests of the German Social Accident Insurance Institution for the raw materials and chemical industry (BG RCI) revealed the need for a systematic study. This investigation was carried out by BG RCI together with the Fraunhofer Institute for Environmental, Safety, and Energy Technology UMSICHT, actively supported by a wide range of experts.

For 1:1-scale tests, a dummy was equipped with conductivity sensors. Low- and high-viscosity liquids served as model contaminants. 15 emergency shower heads of German and international producers, currently used in Germany, were operated at a water volume flow rate from 20 to max. 110 l/min. Along with static tests, using a fixed experimental set-up, dynamic tests have been carried out simulating the relative motion between the accident victim and the shower head. Small-scale tests supported the selection of model contaminants.

Based on the conductivity signals, the time-dependent local dilution of the model contaminant in the course of the showering procedure was recorded. The time needed to achieve a pre-defined reference dilution at a pre-defined percentage of the sensors served as a basis for determining a characteristic wash-off time, providing a criterion for the wash-off efficiency in each single showering test. The reference dilutions were derived from the GHS criteria for the effects of hazardous substances.

Contact persons: Dr. Thomas H. Brock, BG RCI, Dr. Volker Heil and Dr. Ulrich Seifert, Fraunhofer-Gesellschaft, Dipl.-Ing. Hermann Philipp, BASF SE. 

Figure 1:         

Characteristic wash-off time for high-viscosity, water-soluble model contaminants (approx. 250 g) applied to the chest and head of the bare dummy; fixed arrangement of shower head and dummy;
results for 15 shower heads and 20-110 l/min volume flow rate;
categories of spray patterns:
»near-standard«: 40 ‑ 60% of the water within a circle, d=400 mm, located 700 mm below the shower head, according to EN 15154-1:2006;
»outward«: more than 70% outside this circle,
»narrow«: more than 70% within this circle.

Regarding the ensemble of all shower heads used in the test, the characteristic wash-off time did not correlate systematically with the water volume flow rate for water-soluble contaminants (see Figure 1). According to these results, an improvement of the wash-off effect is not to be expected in general when increasing the water volume flow rate of overhead emergency showers to more than 30 l/min.

Spray patterns that led to particularly short characteristic wash-off times do not comply with EN 15154-1:2006 requirements concerning the radial water distribution.

Furthermore, the survey revealed some indications how to act most efficiently in case of the contamination of persons. These suggestions will shortly be discussed, and occupational safety professionals will be informed (e. g. via

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