Ammonia is aggressively corrosive toward body tissue. Because ammonia is extremely hygroscopic, it migrates preferentially to areas on the body high in moisture, including eyes, throat, lungs and dermal areas with elevated wetness (armpits, crotch, etc.). Exposure to ammonia vapor tends to target those high moisture areas, causing chemical burns. Exposure to liquid ammonia can cause chemical and freeze burns due to the combined effects of ammonia's alkalinity and low temperature at atmospheric pressure (-28oF [-33oC]).
Most material safety data sheets (MSDS) for anhydrous ammonia recommend immediately flushing exposed areas with water for at least 15 min; some recommend a 30-min decontamination period. The eye wash and shower station is an essential tool to accomplish the recommended decontamination.
Often, the true functionality of an eye wash and shower station is not tested until an exposure occurs. Any weaknesses in this important safety system will erode the benefit it is attempting to provide. Here is a look at sources providing guidance.
Pertinent RegulationsThe Occupational Safety and Health Administration (OSHA) has two regulations that refer to the need for eye wash and shower stations. The first is published in _CFR 1910.151(c) Medical Services and First Aid, which states:
Where the eyes or body of any person may be exposed to injurious corrosive materials, suitable facilities for quick drenching or flushing of the eyes and body shall be provided within the work area for immediate emergency use.
Similar guidance is provided in CFR 1926.50(g). Because of anhydrous ammonia's corrosive characteristics, 1910.151 is an applicable regulation in plants that utilize ammonia refrigeration systems.
In addition, other codes and standards identify the need for emergency eye wash stations and showers. Section 126.96.36.199 of ANSI/IIAR 2 - 1999 Equipment, Design, and Installation of Ammonia Mechanical Refrigerating Systems states:
An eye wash and body shower unit shall be located just outside the machinery room exit door, and it is recommended that one be located centrally inside the machinery room.
Section 4.3(b) of IIAR Bulletin 112 Ammonia Machinery Room Design states:
Because of the potential for eye and skin exposure to ammonia, accessible eye wash and body shower facilities shall be provided. Because of the importance of quick flushing of the eyes in the event of a spray or splash of liquid ammonia, eye wash facilities should be located in the area of the machinery room.
ANSI Z358.1 - 1998 Emergency Eye Wash and Shower Equipment is a guideline for the proper selection, installation and maintenance of emergency decontamination equipment. Although not widely recognized in the industrial refrigeration arena, ANSI Z358.1 can serve as a useful guideline for documenting and specifying the design, performance, installation, use, training and maintenance of emergency eye wash and shower stations.
LocationANSI Z358.1 requires locating emergency eye wash and shower stations in an area reachable within 10 sec following an exposure event. The emergency equipment also must be installed on the same level as the posing hazard with the travel path free from obstructions.
These requirements can present particular problems for many facilities that utilize ammonia industrial refrigeration systems. For example, several plants have asked: What is the best approach for providing this emergency equipment in areas near evaporative condensers, which typically are roof-mounted? Should permanently piped shower stations be installed on the roof? Should a portable shower station be placed on the roof for access during service work?
Some plants have elected to install permanently piped shower stations on their roof. In northern climates, roof-mounted emergency showers need to be protected from freezing. Another option that warrants consideration is a portable eye wash/shower station.
Supply WaterIn many situations, emergency eye wash and shower stations are piped directly from a plant's potable cold water source. Depending on the location of the plant and the time of year, the temperature of potable water supply will range between 45 and 65oF (7 and 18oC). Keeping in mind that most medical guidance suggests that exposed surfaces of the body be flushed for a period of at least 15 min, it becomes all too clear that sustaining a 15-min dwell time when using water at temperatures below 55oF (13oC) virtually is impossible. In some cases, exposure to cold water can exacerbate the health hazard to the injured, contributing to shock or hypothermia.
ANSI Z358.1 requires tepid water to be delivered for emergency decontamination purposes. Supply water temperatures in the 78 to 92oF (26 to 33oC) range generally are desirable to achieve the tepid recommendation.
Control ValvesThe shower or eye wash station must have an on/off control valve that stays open once actuated until intentionally (i.e., manually) turned off. This allows the individual to remove clothing or hold open eyelids for decontamination without having to simultaneously hold open a valve.
Freeze ProtectionIn cases where the temperature of the installed shower can drop below 32oF (0oC), freeze protection is required.
Maintenance, TrainingTest the eye wash and shower stations quarterly to ensure their functionality. A more extensive evaluation should be conducted on an annual basis to ensure compliance with the flow and water distribution requirements outlined in ANSI Z358.1. Employees who are at risk of exposure to the hazardous chemicals require training in the proper use of eye wash and shower stations.
Drain WaterThink about where the resulting drain water will go. The contaminated water should not create its own hazard. Consider the applicable local, state and federal regulations related to the disposal of the drain water.
Stick to the standard, and consider re-evaluating your eye wash and shower stations to achieve performance in accordance with it. PCE
This article originally appeared in Industrial Refrigeration Consortium's newsletter, The Cold Front, Fall 2001, and is reprinted with permission.
Industrial Refrigeration Consortium (IRC) is a nonprofit university-industry partnership in the College of Engineering at the University of Wisconsin-Madison. Formally established in January of 2001, the IRC provides technical assistance and education services to industrial refrigeration end-users. The IRC also carries out applied research to help advance the state-of-knowledge in the industrial refrigeration industry.