Portable generators are gasoline-powered equipment used to generate electricity for various construction tools and equipment and can present various hazards if used incorrectly.  The common causes of injuries and fatalies that arise from using these equipment are electrical and fire hazards and exposure to carbon monoxide.  This solution outlines some general safe work practices to help reduce these hazards for the user and utility line workers if they are working to restore power during an outage.

Work Practices to Reduce Electrical and Fire Hazards

In order to help prevent electrical hazards, always maintain and operate portable generators (figure 1) according to the manufacturer's guidelines and recommended use such as utilizing ground-fault circuit interruptors. In general, it is important to plug electrical appliances directly into the generator using the appliance manufacturer's cords. In the event that extension cords need to be used, be sure they are heavy-duty and are of the grounded type (3-pronged). They must be rated for the application and the load to be served to avoid overloading the extension cord.  Caution must also be taken to avoid exceeding the capacity of the generator. In addition, always uncoil cords and lay them in flat open locations as cords can get hot and become a fire hazard.

Figure 1. Portable generator. (Photo courtesy of ELCOSH)

Proper grounding and bonding can help prevent electrical hazards from using portable generators.  Under OSHA 29 CFR 1923.404, the generator's frame itself may serve as the ground without the need to use a grounding electrode system (such as a ground rod).  The reason is because the generator's noncurrent-carrying metal components (such as the fuel tank, the engine, and the housing) and the component's grounding conductor terminals are typically bonded to the generator's frame.  However, if there is no bonding of these components, then a grounding electrode system is required.

It is NEVER recommended to connect portable generators directly to the electrical main panel of a structure.  In the event of a power outage, never backfeed a generator to the home electrical wiring system since this could result in backfeeding utility lines endangering utility workers trying to restore normal power. Temporary connections of this type can feed electrical power back through the main breaker to the transformer, which then converts it back to high voltage and can energize the connected utility lines.  Thus, when utility line workers are restoring power, they are subject to the risk of electrocution. Conversely, if normal power is restored, the utility power can backfeed to generator which may cause a potential electrical arc which could result in fire and explosion since portable generators have integral mounted gasoline tanks.  If a portable generator must be connected to a structure, then the electric power must be connected through a power transfer switch (properly installed by a qualified electrician) to isolate the utility systems from the home electrical wiring. The portable generator must also be bonded to a grounding electrode system if used in this manner.

Work Practices to Reduce Carbon Monoxide Exposure

Recognizing carbon monoxide (CO) toxicity symptoms and monitoring CO levels while using gasoline-powered portable generators are work practices that can reduce or eliminate health risks from CO exposure.  The exposure levels will vary depending on the type of ventilation and work setting.  Because of this variability and the ability of CO to accumulate without warning, it is recommended that users follow some general guidelines:

• Not operate portable generators indoors or in partially-enclosed areas unless the engines can be located outside away from air intakes so that engine exhaust is not drawn indoors where the work is being done.  However, an exception to this rule might be during an emergency rescue situation in which other options are not available provided that equipment operators, assisting personnel, and the victim are donning supplied-air respirators
• Learn to recognize the signs and symptoms of CO overexposure which may include headache, nausea, weakness, dizziness, visual disturbances, changes in personality, and loss of consciousness
• Use personal CO monitors (see below) where potential sources of CO exist. These monitors should be equipped with audible alarms to alert workers when CO concentrations are too high or when it exceeds the NIOSH CO Ceiling limit at 200 parts per million

Personal CO Monitoring Instruments

While this is not a comprehensive list of commercially-available options, here are a couple of personal CO monitors from two manufacturers:

SENSIT P100 Personal CO Monitor

• Measuring Range (PPM): 0-999
• Visual, vibrating, and 90 dB audible alarms for high, low, STEL (Short Term Exposure Limit), and TWA (Time-weighted Average)
• Datalogging: Up to 100 alarm events (downloaded through SmartLink Software)

BW Technologies GasAlert Extreme Single Gas (CO) Monitor

• Measuring Range (PPM): 0-1000
• Visual, vibrating, and 95 dB audible alarms for high, low, STEL (Short Term Exposure Limit), and TWA (Time-weighted Average)
• Approved for Class I, Div 1 and CLass II, Div 1 environments
• Replaceable batteries and sensors
• Includes calibration cap and hose
• Optional: BW Technologies Infrared Connectivity Kit and Software is available for linking to a computer for data downloads and access to instrument set up options

• Before the use of portable generators, inspect for damage or loose fuel lines
• Always keep portable generators dry and never operate under wet conditions

Le, Jean Christophe, MPH - CPWR - The Center for Construction for Research and Training

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