Flushing Water Delivery Temperature to Safety Equipment in Laboratories

The information provided in this article is for educational and informational purposes only and should not be construed as medical advice. Always consult with a qualified medical professional or industrial hygienist for appropriate first aid treatment and the management of workplace risk factors.

Plumbed first aid equipment in the laboratory workspace is vital for flushing harmful chemicals from the skin and/or eyes and must support therapeutic treatment over a prolonged period.

Architects, laboratory design consultants, and engineers collaborate with stakeholders to design workspaces for scientists and medical researchers. The spaces must support the workflow, environmental conditions, and utilities required to perform their tasks, many of which involve handling corrosive and injurious materials. Beyond personal protective equipment (PPE), a laboratory's most significant safety equipment is plumbed first aid devices such as safety showers and eye/face wash fixtures. Laboratory hazards and the first aid equipment provided in workspaces are subject to the oversight of local, state, and federal regulations.

The top of the workplace regulatory hierarchy in the US is the Occupational Safety and Health Administration (OSHA). Although OSHA holds the highest authority in workplace safety enforcement, its regulations can be the most vaguely worded. For example, OSHA Standard 29 CFR 1910.151(c) 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."

Many factors must be taken into consideration when determining what qualifies as “suitable facilities.” One nationally recognized standard is ANSI/ISEA Z358.1 “Emergency Eyewash and Shower Equipment.” This ANSI standard provides detailed requirements on the performance, installation, use, and maintenance of this equipment.

The ultimate purpose of this equipment is to deliver flushing fluid (potable water) to the skin or eyes to treat chemical or thermal burns. Critical factors that must be addressed are flow, pressure, temperature, and water quality, among others. Each factor is a subject unto itself, but this article focuses on delivery temperature.

ANSI/ISEA Z358.1, Appendix B, Section 6 states, “While cold flushing fluid temperatures provide immediate cooling after chemical contact, prolonged exposure to cold fluids affects the ability to maintain adequate body temperature and can result in premature cessation of first aid treatment.” Other than offering an upper and lower limit for delivery temperature (60°F to 100°F or 16°C to 38°C), ANSI leaves designers to determine the proper design conditions for safety equipment delivery temperature, and advice from the scientific and medical community can be informative.

OSHA’s Hazard Communication Standard (29 CFR 1910.1200(g)) requires that chemical manufacturers, distributors, or importers provide Safety Data Sheets (SDSs) (formerly MSDSs or Material Safety Data Sheets) for each hazardous chemical to downstream users. Section 4 within these SDS documents provides recommendations for immediate medical care and special treatment upon exposure to the chemical on the skin and in the eyes. A typical statement may say:

Skin Contact: Immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Call a physician, immediately. Wash clothing before reuse.

Eye Contact: Immediately flush eyes with plenty of water for at least 15 minutes, lifting lower and upper eyelids occasionally. Get medical attention immediately.

The phrase “plenty of water for at least 15 minutes” cues designers and facilities managers to provide flushing equipment for first aid use in the workspace. However, a recommended delivery temperature is not specified.

While the American Burn Association (ABA) does not provide detailed guidelines specifically for the operation of plumbed first aid equipment, it emphasizes the importance of immediate and proper first aid for burns. This includes the recommendation to use cool water for initial treatment for about five minutes. This immediate intervention helps to reduce the temperature of the burn, minimizing tissue damage and relieving pain. However, for safety showers and eyewashes specifically, the prolonged use of tepid water (not cold) is recommended to prevent additional injury from extreme high or low temperatures.

The transition from cool water at the onset of treatment to a tepid level (also referred to as “tempered”) is critical to maintain the recommended 15-minute flushing duration. Consider the discomfort of taking a cold shower at home. While a typical household showerhead flows at a rate of 2.5 gallons per minute, an emergency shower flows at a rate of 20 gallons per minute at a minimum. Cases have been documented where an injured worker had to be physically held under the shower to maintain flushing. The same is true for eyewashes, where cold water can feel painful.

According to the Academy of Aquatic Physical Therapy (APTA), a water temperature range of 79°F to 84°F (26°C to 29°C) is recommended for aquatic therapy to support patient comfort, muscle relaxation, and manage blood pressure. Sustained exposure to cold water (typically below 68°F or 20°C) can lead to adverse physiological effects, particularly when a person is already under physical or mental stress from a chemical or thermal burn. Cold shock can cause a sudden increase in heart rate (tachycardia) and blood pressure due to the release of stress hormones like adrenaline. Cold water immersion can impair cognitive function, leading to confusion, impaired judgment, and decreased ability to perform complex tasks, which is particularly dangerous in a crisis.

Figure 2: Flushing water temperature profiles. Image: John Rattenbury

The recommended design behavior of a flushing fluid system can be summarized as follows:

1.     The initial flushing should be done with cool (not cold) water, ideally at a temperature of around 60°F to 77°F (15°C to 25°C). Starting with water at ambient room temperature is acceptable which will be the equilibrium temperature of flushing water in the supply pipe, about 72°F (+/-2°F). Do not use ice-cold water as it can cause vasoconstriction, which may exacerbate tissue damage.

2.     The initial cool water flushing should be applied for about five minutes. For chemical burns, it may need to be longer, ensuring all traces of the chemical are washed away.

3.     After the initial cooling phase, transitioning to warmer water will help with comfort and continued pain relief. This occurs as the propagation of water from the supply mixing valve through the supply piping reaches the plumbed first aid equipment as the ambient temperature water is discharged.

4.     The water temperature gradually increases to a comfortable level, typically around body skin temperature of 85°F (30°C) or slightly warmer but should not exceed 100°F (38°C).

5.     Sustained flushing with warmer water can continue for an additional 20-30 minutes, or until pain relief is achieved. In some cases, longer durations might be beneficial, especially for deeper or more extensive burns so the burn victim can tolerate continued flushing of the skin until a first aid professional can arrive.

To support this temperature delivery profile, the water in the piping may be at ambient temperature. However, the water service pipe from the city supply to a building is at ground temperature which is 52°F to 65°F (11°C to 18°C) in North America. Continued supply of flushing water without temperature control will lead to low water delivery temperatures with adverse physical effects. This is why plumbing engineers provide a hot water source and a mixing valve to provide a sustained delivery temperature of 30°C (85°F), which is a more therapeutic temperature to support continued flushing. These valves are specialized for tempered water systems and are required to be compliant with ASSE 1071, “Performance Requirements for Temperature Actuated Mixing Valves for Plumbed Emergency Equipment.”

In conclusion, plumbed first aid equipment in the laboratory workspace is vital for flushing harmful chemicals from the skin and/or eyes and must support therapeutic treatment over a prolonged period. Flushing fluid temperature must be delivered at controlled temperatures to support this treatment. Proper communication between the design team and stakeholders is important to ensure the plumbing design is appropriate and the effects of delivery temperature on the body are understood.

John M. Rattenbury is a registered professional mechanical engineer in Massachusetts and several other states. He holds a Certified in Plumbing Design (CPD) credential from the American Society of Plumbing Engineers. He has been practicing in the field of plumbing engineering since 1993 and is currently a senior engineer at R. G. Vanderweil Engineers, LLP in Boston, Massachusetts.