Keeping the water flowing:

Strategies for meeting the ANSI full-flush requirement

By Nate Kogler, Bradley Corporation

Employees working with chemicals, hazardous materials and flying debris put their health at risk on the job every day. Increased use of hazardous chemicals across many industries is putting an increasing number of workers in harm's way. It is not just heavy industrial applications; chemicals found in janitorial closets and photo labs can pose serious health risks.

Specifying emergency safety equipment is not just a matter of meeting regulations. Selecting the best safety solutions and installing them in appropriate locations that aid workers in immediately flushing the affected area can mean the difference between an unfortunate but relatively minor injury and scarring or even permanent blindness.

Choosing the right solution

One of the most critical, but often overlooked, aspects of properly selecting and installing an emergency fixture is making sure that the fixture is certified to the American National Standard Institute (ANSI) standard for emergency equipment and that it is capable of delivering a full 15-minute flush. While emergency fixtures may look similar, it does not mean that their quality or performance capabilities are equal. Only an independent, third-party organization can confirm that a manufacturer's product is certified to the ANSI Z358.1-2004 standard.

Well-known manufacturers clearly document compliance with ANSI standards because the testing and requirements are so important. ANSI-certified products generally come with important installation information, such as mounting heights for the eyewash or drench shower, to ensure that the fixture is compliant. Moreover, the equipment meets the minimum performance requirements provided; other products simply may not provide the necessary flushing requirements.

Drench shower vs. eyewash units

Beyond identifying quality products, there is often confusion about whether to select a drench shower, an eyewash unit or a combination fixture that has both a shower and eyewash. Safety systems are generally intended to perform a few key functions: diluting chemical compounds, irrigating the eyes or other affected area and/or extinguishing a fire. The best type of fixture depends on the specific workplace hazard and the area of the body or face that could be affected by that hazard.

An eyewash or eye/face wash unit is usually appropriate if the concern is limited to the eyes or face. If a larger part of the body is at risk for exposure or potential injury, a drench shower should be installed. It is worth noting that a drench shower does not replace an eyewash unit. The flow of a drench shower is not designed to adequately flush the eyes, so if there is a risk to the eyes, a combination fixture or separate eyewash or eye/face wash should be installed.

When the body is to be flushed following chemical contact, clothing must be removed after the shower has been activated. Even in an emergency, privacy can be a concern for the user. Consider installing a privacy curtain around the shower to shield users from prying eyes and to help them focus on rinsing themselves, rather than trying to cover themselves because they are self-conscious.

Flow and drainage issues

During installation, it is important to consider water flow and adequate drainage. Showers can produce a large volume of wastewater over a 15-minute flushing period and during routine weekly testing. A drench shower will deliver a minimum of 300 gallons of water in just 15 minutes.

Provisions for adequate drainage should be provided, whether the unit is part of the original building plans or added later. If the drench shower or eyewash is activated and drainage is not present, water collecting around the unit may contaminate other work areas, cause slipping for users or respondents or result in costly water damage to the building. Local authorities should be consulted to determine whether the wastewater can be routed with other wastewater from the building or whether special provisions should be made. This may depend on the chemicals being used in the environment, the potential concentration of chemicals being flushed from the user and local codes and standards.

On the incoming side, the water supply should be a minimum of 30 pounds per square inch (psi), as required by ANSI. The size of the incoming supply pipe should be indicated in the manufacturer's installation instructions. If incoming pipes are undersized, an adequate volume of water may not be provided to the product, especially if the water pressure is low.

Drench showers should provide a minimum flow of 20 gallons per minute (gpm) and eyewashes a minimum of 0.4 gpm. Most plumbed eyewashes require a flow rate closer to 3 - 4 gpm for a suitable eyewash pattern, as required by the ANSI Z358.1 standard.

Tepid water requirements

To ensure that users are able to flush the affected area with water for 15 minutes or longer, ANSI Z358.1-2004 was updated to include a tepid water requirement. Water temperature plays an important role in ensuring that someone will shower long enough to remove hazardous chemicals or debris. At frigid temperatures, most people will not rinse long enough; those that do are at risk of hypothermia. On the other hand, hot water can cause scalding or could accelerate a chemical reaction and cause further tissue damage.

Providing a tepid flow of water in all new and existing systems helps protect workers. The ANSI standard now defines the upper and lower limit of recommended water temperatures to keep water "moderately warm; lukewarm." The appendix explains that the lower temperature limit should be about 60 F, and that water over 100 F could enhance interaction of the chemical with the skin and be harmful to the eyes. To determine the proper temperature for the application, MSDS sheets should be consulted. If further information is needed, an industrial hygienist or physician should be contacted.

Older emergency fixtures originally supplied with only cold water can be retrofitted. The best solution for controlling the incoming water temperatures with a high degree of accuracy is to install a thermostatic mixing valve designed for emergency fixtures.

TMVs for emergency applications

Thermostatic mixing valves (TMVs) blend hot and cold incoming water to achieve the appropriate outlet temperature within a preset temperature range. (Note that these temperatures should be set and adjusted by the installer according to the site conditions.) The blended water is then fed to the emergency drench shower or eyewash.

Not all TMVs are created equal. There is a difference between standard thermostatic valves and thermostatic mixing valves designed for emergency fixtures. Standard TMVs are designed to shut off the flow of water should there be a loss to either the hot or cold water supply. This is fine for typical domestic situations, where a supply of only hot or only cold water would shock someone taking a shower. An emergency application is different; it is better for someone to shower in cold water than in no water at all.

To maintain a continuous flow of water, emergency valves are designed with a cold-water bypass. Should the thermostat fail or the valve lose its hot water source for any reason, the cold water would still be allowed to flow through the valve to the emergency fixture. If the cold supply is lost, the valve will shut off and prevent the hot water from flowing through the valve to the emergency fixture. This protects the user from the potential dangers of hot flushing fluid being supplied to the eyewash or shower.

The thermostat continually measures the temperature of the mixed water flowing through the TMV to ensure a consistent temperature. If the temperature differs from the valve's set temperature, the thermostat will react and move a mechanism that modulates one or both of the inlet ports until the valve returns to the set temperature, thus ensuring that each emergency fixture is provided with tepid water.

Sizing thermostatic mixing valves

When selecting the appropriate valve, particularly for emergency showers that use a high volume of water, it is critical to size the valve for each particular application. There are several important criteria. One is the maximum flow demand on the valve. Another is the minimum incoming flow rate required to maintain the appropriate set temperature. If the valve will feed more than one fixture, it should be sized to provide the appropriate amount of water to all eyewashes and drench showers simultaneously.

According to ANSI, the minimum flow rate for a drench shower is 20 gpm at 30 psi. Eye/face wash units require a lower volume of water with a minimum of 3 gpm at 30 psi. Smaller emergency fixtures, such as eyewash units, require just .4 gpm at 30 psi.

With a combination drench shower and eye/face wash, a valve capable of supplying tepid water at a rate as low as 3 gpm or as high as the combined flow rate of the drench shower and the eye/face wash (a minimum of 23 gpm at 30 psi, but maybe more) would be required. Valve sizes should be based on the emergency fixture manufacturer's actual flow rates, as many of the products on the market exceed the ANSI Z358.1 standard.

Most valve manufacturers offer TMVs in different sizes to meet the flow requirements of the various emergency fixtures. Flow rates of each valve under normal operation or cold-water bypass operation should be clearly provided. To ensure that a victim is protected in an emergency, select a valve that provides enough water through its cold-water bypass to meet the emergency fixtures minimum water requirements.

Specifying the appropriate emergency fixture and correctly sizing a TMV to deliver tepid water to emergency applications does not need to be complicated. Choosing a TMV manufactured by the same company that supplies the ANSI-approved drench shower or eyewash equipment is one easy way to save time and avoid headaches. Consulting with product manufacturers and emergency safety experts can help ensure the perfect fit for your next application and ultimately help workers down the road that may need to activate that shower and use it for at least 15 minutes.

Nate Kogler is a product manager for Emergency Fixtures at Bradley Corporation, a leading manufacturer of plumbing fixtures, washroom accessories, restroom partitions, emergency fixtures and solid plastic lockers. He can be reached at Bradley Corp., W142 N9101 Fountain Blvd., Menomonee Falls, WI 53052-0309. For more information, call 800/BRADLEY or visit www.bradleycorp.com.