Have you ever wondered what’s responsible for the bright lighting in commercial areas? Most often, metal halide or mercury vapor lights are responsible for the glow. These long-lasting lights are have many uses, including:
- Street lights
- Gyms
- Sports arenas
- Banks
- Mercantile
- Warehouses
- Industrial locations
What’s inside?
Metal halide bulbs have double tube construction. The inner layer is a quartz arc tube containing mercury vapor metal and halides — which is contained in an outer glass tube. An electric arc moves through the gaseous mixture of vaporized mercury and metal halides to produce high-intensity light. The outer glass tube filters out the harmful, short wavelength ultraviolet (UV) radiation produced within the inner tube.
The bulbs produce light between 75 to 100 lumens per watt and have a lamp life of 6,000 to 15,000 hours. As a result, these lights are the fastest-growing segment in the lighting industry.
Types of bulbs
Currently, two major types of halide and mercury vapor light bulbs are sold in the U.S:
T-type lightbulbs — these bulbs have a self-extinguishing feature within 15 minutes after the outer bulb is broken. T-type lightbulbs may be used in open or enclosed fixtures.
R-type lightbulbs — these bulbs aren’t self-extinguishing. R-type lightbulbs should only be installed in light fixtures that are fully enclosed by glass or plastic lens to shield people from the UV radiation. They can also be placed in areas where people will not be exposed to UV radiation if the outer bulb breaks.
Safety first
While these lights are powerful, they can also be dangerous. Hazardous conditions may occur when the outer tube is broken or cracked, and the inner tube continues to function. Under these conditions, intense, short wavelength UV radiation is allowed to escape. The escaping radiation can negatively impact the health of nearby workers. Exposure to this UV radiation can cause:
- Eye and skin burns
- Blurred or double vision
- Headaches and/or nausea
- Long term cornea damage
Recommendations
For safety, the U.S. Food and Drug Administration recommends:
- Replacement of non-self-extinguishing R-type high intensity metal halide and mercury vapor lightbulbs used in open or wire grid fixtures with self-extinguishing T-type lightbulbs
- Replacement of open-wire grid fixtures with self-extinguishing T-type lightbulbs
In 2005, the National Electrical Code began requiring that bulbs at risk for physical damage, such as in gyms, sports facilities, all-purpose facilities, etc., must be fully enclosed by a glass or plastic lens. Fully enclosing fixtures, or using self-extinguishing T-type lightbulbs, is the best way to reduce the risk of burns.
Identifying exposure
The National Electric Code also began to require labeling on all fixtures in 2005. Since labels can be removed or obscured, it’s important that contractors facing potential exposure are aware of the safety hazards.
Exposure occurs when working near a bulb that has been damaged, but isn’t self-extinguishing. If the employee works near the operating bulb, they can experience the significant health risks mentioned previously. Those exposed most frequently include:
- Electricians
- HVAC duct hangers and installers
- Low voltage installers
- Fire protection installers
- Painters
- Plumbers
- Drywall installers
- Lighting installers
- Maintenance workers
Construction tips
These lights present a unique challenge for the construction industry specifically. As the fastest growing lighting segment, metal halide bulbs are becoming popular as temporary lighting on jobsites. Contractors should take special care to label the area near the lights and inform site personnel of the appropriate actions, should an emergency occur.
To discover more trends and tips for the jobsite, visit our risk management .
