Montgomery County, MD Noise from Specific Sources: HVAC & Mechanical Noise (2026)
Key Facts
- Property-line limit
- 60 dBA (55 dBA if tonal)
- Applies to
- lots under 12,000 sq ft
- Pre-1989 units
- 65 dBA allowance expired 1999
- Enforcing agency
- Dept. of Environmental Protection
- Civil penalty
- $500 first, $750 repeat offense
Summary
Outdoor heat pumps and A/C units on small residential lots in Montgomery County must meet a strict 60 dBA property-line limit, enforced under a dedicated executive regulation, not the general noise code.
The maximum permissible sound level at the property line for the outdoor unit of any heat pump or air conditioner located on residential lots less than 12,000 square feet in area must not exceed 60 dBA. If the sound is determined to be a tonal noise as defined in 31B.00.03.03, the maximum permissible sound level at the nearest property line must not exceed 55 dBA.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-90: Montgomery County Code contains legislation effective through May 7, 2026 | Zoning Updated Effective: April 13, 2026 | COMCOR Regulations effective as of July 1, 2026).
Full Breakdown
COMCOR 31B.00.03 sets a hard cap on outdoor heat pump and air conditioner noise for houses on lots under 12,000 square feet: 60 dBA at the property line, dropping to 55 dBA if the unit produces a tonal whine or hum. Units made before July 1, 1989 got a temporary 65/60 dBA allowance that expired in 1999. It doesn't cover non-residential buildings, apartments over 30 feet tall, or condos where the unit and the affected neighbor share the same building. Everything else defaults to the county's general 65/55 dBA noise-area limits under Sec. 31B-5.
Violations & Fines
Exceeding the property-line limit is a violation of Sec. 31B-5(b)(2) and a Class A civil violation: up to $500 for a first offense, $750 for a repeat one, or a criminal fine up to $1,000.
Frequently Asked Questions
Does this apply to every AC unit in the county?
Can I get an exemption if my unit can't comply?
Sources & Official References
Other rules in Montgomery County
Compare Montgomery County to another location·View the Maryland noise from specific sources overview
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