Lightning is a serious hazard for outdoor workers, particularly those working in open areas, at elevated locations, or around equipment and structures that may be exposed during thunderstorms. Lightning can strike several miles away from the heaviest rainfall, putting workers at risk even when a storm does not appear to be directly overhead.
Recognizing approaching thunderstorms, knowing where to seek safe shelter, and stopping outdoor work before conditions become dangerous are essential for preventing lightning-related injuries and fatalities.
Lightning Hazards at Work
Lightning is a dangerous natural force. According to OSHA, in the United States, over 300 people are struck by lightning every year and unfortunately many of those people die from their injuries.
Lightning is a giant spark of electricity in the atmosphere between clouds or between a cloud and the ground. Thunderstorms always include lightning and any thunder you hear is being caused by lightning.
Jobs at High Risk for Lightning Strikes
Workers whose jobs involve working outdoors in open spaces, on or near tall objects, or near explosives or conductive materials have significant exposure to lightning risks. Worker activities at higher risk for lightning hazards include:
- Heavy Equipment Operation
- Roofing
- Power Utility Field Repair
- Construction/Scaffolding Work
- Steel Work/Telecommunications
- Explosives Handling or Storage
- Plumbing and Pipe Fitting
- Building Maintenance
- Logging
- Farming and Field Labor
- Lawn Services/Landscaping
- Airport Ground Personnel Operations
- Pool and Beach Lifeguarding
Although certain occupations have greater exposure to lightning hazards, anyone working outdoors can be at risk when thunderstorms develop. Workers should not assume they are safe because they are working at ground level, the rain has not started, or the storm appears to be some distance away.
Employers should consider lightning exposure when planning outdoor activities and make sure workers can quickly reach appropriate shelter when thunderstorms approach.
Recognizing Thunderstorm Warning Signs
Before and during outdoor work, check local weather reports and keep an eye out for darkening clouds and increasing wind speeds, which can indicate developing thunderstorms. Lightning is unpredictable and can strike outside the heaviest rainfall areas or even up to 10 miles away from any rainfall.
Many lightning victims are caught outside during a storm because they did not act promptly to get to a safe place, or they go back outside too soon after a storm has passed.
If there are signs of an approaching thunderstorm, workers should not begin any task that they cannot quickly stop if they need to get to safety. If you hear thunder when working outdoors, even a distant rumble, get to a safe place immediately.
Although OSHA does not have a general standard specifically addressing lightning exposure, employers are responsible for protecting workers from recognized hazards, including dangerous weather conditions.
OSHA General Duty Clause 5(a)(1) Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.
Employers should establish procedures for monitoring thunderstorms, suspending exposed outdoor activities, communicating weather warnings, and identifying safe shelter locations. Workers should understand these procedures before work begins and have enough time to reach shelter when lightning threatens the area.
Work Restrictions During Storms
Certain construction activities become especially dangerous during thunderstorms, high winds, and other severe weather conditions. Workers may be exposed to lightning, unstable equipment, falling materials, and an increased risk of falls.
OSHA has specific restrictions for certain activities during hazardous weather:
- Scaffolding: OSHA Standard 1926.451(f)(12) prohibits work on or from scaffolds during storms or high winds unless a competent person determines that it is safe and employees are protected by a personal fall arrest system or wind screens. Wind screens may only be used when the scaffold is secured against the anticipated wind forces.
- Crane Operations: OSHA Standard 1926.1417(n) requires employers to follow the manufacturer's recommendations for operating in windy conditions. If manufacturer recommendations are unavailable, a qualified person must determine whether operations can proceed safely. OSHA also requires employers to address adverse weather conditions, including lightning, when they affect equipment operation or the handling of loads.
- Masonry Wall Construction: OSHA Standard 1926.706(a) requires a limited access zone whenever a masonry wall is being constructed. OSHA also has requirements for bracing masonry walls to prevent overturning and collapse. However, these provisions do not establish a general prohibition on working on top of walls during thunderstorms.
Regardless of the type of work being performed, outdoor activities that expose workers to lightning should be suspended when thunder is heard or lightning threatens the work area. Workers should not remain on scaffolds, rooftops, elevated platforms, or around cranes and other large equipment while attempting to finish a task.
Employers should establish clear stop-work procedures so employees know when to discontinue activities, secure equipment when it is safe to do so, and move to an appropriate shelter. Work should not resume until at least 30 minutes after the last sound of thunder and other hazardous weather conditions have passed.
Safe Shelter from Lightning
Outdoor workers should know ahead of time where to go if the weather turns dangerous and they need to get to safety. NOAA recommends workers seek out fully-enclosed buildings with electrical wiring and plumbing. In modern buildings, the interior wiring and plumbing will act as an earth ground.
A building is a safe shelter as long as you are not in contact with anything that can conduct electricity like electrical equipment or cords, plumbing fixtures, and corded phones. Do not lean against concrete walls or floors which may have metal bars inside.
If safe building structures are not accessible, workers can seek shelter in hard-topped metal vehicles with the windows rolled up. Remain in the shelter, or vehicle, for at least 30 minutes after hearing the last sound of thunder.
After hearing thunder, do not use corded phones, except in an emergency. Cell phones and cordless phones may be used safely.
Emergency Planning and Awareness
All workers should be informed on and understand inclement weather policies and procedures. People are most commonly struck by lightning at the beginning or ending of a thunderstorm, outside of heavy rain, and in smaller storms, when they have a false sense of security and tend to take more chances.
A competent person should evaluate the site before work begins and throughout the workday to ensure a safe working environment that is free of hazards, including dangerous weather. If there is not a competent person on site to evaluate and inform on hazards, or if a worker is alone, then audio or visual contact should be provided, especially during inclement weather.
Reduce Lightning Strike Risk Outside
If workers are caught outside during a thunderstorm with no safe place available to retreat to, NOAA recommends the following precautions to take to decrease a worker’s risk of being struck by lightning.
Lightning is likely to strike the tallest objects in a given area—you should not be the tallest object. Avoid isolated tall trees, hilltops, utility poles, cell phone towers, cranes, large equipment, ladders, scaffolding, or rooftops. Avoid open areas like fields. Never lie flat on the ground.
Retreat to a dense area of smaller trees that are surrounded by larger trees or move to a low-lying area like a valley or ditch but be sure to watch for flooding in these areas. Avoid water, and immediately get out of and away from bodies of water. Water does not attract lightning, but it is a good conductor of electricity.
Avoid wiring, plumbing, and fencing. Lightning can travel long distances through metal. Stay away from metal objects, equipment, and surfaces that can conduct electricity. Do not seek shelter in sheds, pavilions, tents, or covered porches because they do not provide adequate protection from lightning.
Rubber-soled shoes and rubber tires do not provide protection from lightning.
Lightning safety depends on recognizing dangerous weather conditions and taking action before workers are exposed to a thunderstorm.
Monitor weather forecasts, identify safe shelter locations before outdoor work begins, and stop exposed activities immediately when thunder is heard. Never rely on trees, open structures, or equipment for protection, and remain in a safe shelter for at least 30 minutes after the last sound of thunder.
Clear emergency procedures, effective communication, and prompt decisions to suspend work can help prevent serious lightning-related injuries and fatalities.
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