Noise Standards
Commercial buildings are required to have emergency standby generators to operate emergency lights, elevators, fire alarms and fire pumps during power outages. Also, in recent years it has become increasingly popular for homeowners to install emergency standby generators. Consequently, the number of noise complaints related to emergency standby generators has been steadily increasing.
Problems may be avoided through careful planning, design, equipment selection and installation. Almost all manufactured products, including generators, have noise performance specifications. Potential noise sources that can operate on a 24-hour basis, such as standby generators, are required to meet Montgomery County's more restrictive nighttime standard of 55 dBA (A-weighted decibels) at the nearest receiving residential property line.
Things to consider when planning for the installation of an emergency standby electric generator:
- Purchase the quietest generator available. It is much easier to start with equipment that can meet the standard than try to retrofit equipment with noise suppression features later.
- The physical location of the generator should be chosen to minimize noise impacts to both on-site occupants and all nearby neighbors.
- The general rule of thumb is every time you double the distance from a point noise source you get a corresponding 6 dBA drop in sound pressure. Therefore, if the level is 62 dBA at 7m it would be 56 dBA at 14 m, and 50 dBA at 28 m, and so on. Noise measurements are typically taken from a complainant’s closest property line.
- Schedule the recommended periodic testing of generators to occur at times when building occupants and nearby neighbors are least likely to be disturbed.
- The regulations grant a 2.5 dBA allowance for any possible inaccuracies in the sound meter or the operator. The actual nighttime standard is therefore 57.5 dBA or lower.
- If distance is a restricting factor, consider constructing a noise barrier to reduce the sound. Several commercial "noise attenuation" or "acoustic enclosure" solutions are available.
For more information, email DEP at askdep@montgomerycountymd.gov or call 311
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Air Standards
In addition to noise concerns, be aware of the following air quality issues when purchasing or placing electric generators:
- Locate electric generators to minimize exhaust emissions impacts to on-site occupants and all nearby neighbors
- The Montgomery County Air Quality Ordinance, Chapter 3 of the Montgomery County Code, prohibits the discharge of any visible emission (exhaust smoke) from a generator into the atmosphere.
- Give careful consideration to the choices of fuel types (diesel, natural gas, or LP gas) available for your specific generator. There are advantages and disadvantages for each type fuel. Diesel powered generators might be cheaper to operate, but they typically produce more visible emissions and require a large fuel storage tank.
Planning and Permitting Standards
For more information, email DEP at askdep@montgomerycountymd.gov or call 311
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