Mechanical Permit: A permit issued by a local building department authorizing the installation, alteration, or replacement of mechanical systems — primarily heating, ventilation, and air conditioning (HVAC) equipment — required before most HVAC work can legally begin.
When a Mechanical Permit Is Required
Mechanical permits are required for: installing a new furnace, air handler, or heat pump, replacing existing HVAC equipment (even in-kind replacements), installing a new air conditioning system, adding or significantly modifying ductwork, installing a mini-split or ductless system, installing ventilation systems for kitchens and bathrooms, and installing gas appliances beyond portable equipment. Minor maintenance — filter replacement, coil cleaning, refrigerant recharge by a licensed technician — does not require a permit.
Who Pulls Mechanical Permits
Mechanical permits must be pulled by licensed HVAC or mechanical contractors in most states. Some states allow homeowners to pull mechanical permits for their primary residence. The licensed contractor signing the permit is responsible for code compliance. As with electrical and plumbing, never let a contractor "skip the permit" for HVAC work.
What Mechanical Inspections Cover
Mechanical inspections verify: proper equipment installation per manufacturer specifications, adequate combustion air for gas-fired equipment, proper flue and venting connections, refrigerant line installation (for cooling equipment), duct connections and sealing, and electrical disconnect requirements. California's Title 24 also requires verification of duct leakage testing results for HVAC replacements.
Gas Permits
In some jurisdictions, gas line work has its own separate gas permit in addition to — or instead of — a mechanical permit. Gas permit requirements cover installation of new gas lines, extension of existing lines, and connection of new gas appliances. Gas work must be inspected and approved before gas service is restored after the work is complete.