The American Red Cross has developed guidelines for the purchase and safe operation of generators, with technical advice from the Centers for Disease Control and Prevention, the National Fire Protection Association and the U.S. Consumer Product Safety Commission. Homeowners might want to use a generator if they are without power after a storm.

For power outages, permanently installed stationary generators are better suited for providing backup power to a home. Even a properly connected portable generator can become overloaded.

When purchasing a generator, first determine how much power you will need by looking at the labels on lighting, appliances and equipment you plan to connect to the generator. For lighting, the wattage of light bulbs indicates the power needed. Appliances and electrical equipment usually have labels indicating power requirements. Choose a generator that produces more power than will be drawn by the combination of lighting, appliances and equipment you plan to connect. If the generator does not produce adequate power for all your needs, stagger the operating times for various equipment.

If you cannot determine the amount of power that will be needed, ask an electrician. If your equipment draws more power than the generator can produce, then you may blow a fuse on the generator or damage the connected equipment.

The primary hazards to avoid when using a generator are carbon monoxide (CO) poisoning from the toxic engine exhaust, electric shock or electrocution and fire, according to the Red Cross. Follow the directions that come with the generator.

Generators should never be used indoors, including inside a garage, carport, basement, crawlspace or other enclosed, partially-enclosed or ventilated area. Opening doors and windows or using fans will not prevent CO buildup. The CO from generators can rapidly lead to full incapacitation and death, but CO can’t be seen or smelled. Even if you cannot smell exhaust fumes, you may still be exposed to CO. If you start to feel sick, dizzy, or weak while using a generator, immediately get fresh air.

Do not place generators near windows, doors and vents that could allow CO to go inside. To avoid electrocution, keep the generator dry and do not use in rain or wet conditions. To protect the generator from moisture, operate it on a dry surface under an open canopy-like structure. Touch generators with dry hands.

It is a good idea to install battery-operated CO alarms or plug-in CO alarms with battery backup in your home. Test the batteries frequently and replace when needed.

Be sure to turn the generator off and let it cool down before refueling. Gasoline spilled on hot engine parts could ignite.

Store fuel for the generator in an approved safety can that is kept outside of living areas. Use the type of fuel recommended in the instructions or on the label on the generator.

Plug appliances directly into the generator or use a heavy duty outdoor-rated extension cord that is rated (in watts or amps) at least equal to the sum of the connected appliance loads. Check that the entire cord is free of cuts or tears, and that the plug has all three prongs, especially a grounding pin.

Never try to power the house wiring by plugging the generator into a wall outlet, a practice known as back feeding – a dangerous practice that presents the risk of electrocution to utility workers and neighbors served by the same utility transformer. Back feeding also bypasses some of the built-in household protection devices.

The only recommended method to connect a generator to house wiring is by having a qualified electrician install a power transfer switch.