How long should I wait after changing the filter before my AC starts cooling again?

Give the system 20–30 minutes after changing a severely clogged filter. If the evaporator coil froze due to restricted airflow, you may need to let it thaw for 2–4 hours with the system in fan-only mode before full cooling returns.

My AC runs constantly but can't reach the thermostat setpoint on hot days. Is that normal in Fairfax?

On extreme heat days, it's normal for a correctly sized AC to run nearly continuously. If it's running non-stop on a moderate summer day and still can't catch up, you likely have an airflow problem, a refrigerant issue, or a system sizing problem.

Should I turn my AC off if it's not cooling, or keep running it?

If you suspect a frozen coil, switch to fan-only mode or turn the system off. For other issues like a dirty filter or dirty condenser, you can continue running while you address the fix. When uncertain, fan-only is the safest setting.

How do I verify an HVAC contractor is licensed in Virginia?

Virginia requires all HVAC contractors to hold an active license through the Virginia Department of Professional and Occupational Regulation (DPOR). You can verify any contractor's license status on their website.

Is a heat pump a good replacement for a failing AC in Northern Virginia?

Yes — modern variable-speed heat pumps are well-suited to NoVA's Climate Zone 4A. They qualify for the largest federal tax credits available in 2026 and Dominion Energy offers rebates for qualifying installations.

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HVAC Smells Like Gas? Do This Immediately — A Northern Virginia Safety Guide

If you smell gas: get out, don't touch anything electrical, call 911 from outside. The immediate safety steps, the invisible carbon-monoxide danger, and the furnace inspection you need afterward.

September 17, 2026 By the Fairfax Mechanical Team 8 min read

If You Smell Gas Right Now

Act first, investigate later

A gas odor near your furnace or anywhere in your home is a safety emergency. This guidance applies to every home in Fairfax, Alexandria, Arlington, and across Northern Virginia.

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Leave the house right awayGet every person and pet outside to fresh air.
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Don't touch anything electricalNo light switches, thermostats, appliances, or garage-door openers — a single spark can ignite gas. Don't light matches or lighters.
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Don't use your phone insideOnce you're outside and away from the home, call 911 and your gas utility's emergency line.
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Don't go back inNot until emergency responders or the gas company confirm it's safe.

Natural gas is deliberately given a distinctive rotten-egg or sulfur smell so leaks can be detected, so never brush it off. The source could be your furnace, a gas line, the water heater, a stove, or another appliance.

The Related, Invisible Danger: Carbon Monoxide

Unlike that warning gas odor, carbon monoxide (CO) is completely colorless and odorless — you can't sense it at all. It's produced by incomplete combustion, and in HVAC systems the most serious source is a cracked furnace heat exchanger, which can leak combustion gases into the air your system blows through the house.

COColorless, odorless — undetectable by human senses

Every levelWhere CO detectors belong in a home with fuel-burning appliances

MonthlyHow often to test your detectors

Because you can't smell CO, every Northern Virginia home with fuel-burning appliances needs working carbon monoxide detectors on every level and near sleeping areas, tested monthly.

Warning signs of a furnace problem

A yellow (rather than steady blue) burner flame, soot around the unit, and flu-like symptoms without a fever — especially when several people or pets feel sick at once.

After the Emergency Is Cleared

Once professionals have made the home safe, have a licensed HVAC technician inspect the system — including the heat exchanger, combustion, and venting — before it runs again.

A furnace inspection after a gas event isn't paperwork — it's the step that tells you whether the appliance is safe to light again.Fairfax Mechanical Technical Team, Fairfax, VA

Why Call Fairfax Mechanical

We're a licensed Virginia HVAC contractor with EPA-certified technicians serving all of Northern Virginia, and we take furnace safety seriously — from heat-exchanger inspections to complete combustion and venting checks.

Smelled gas and the home is now safe? Book a full furnace safety inspection before it runs again.

Book a Safety Inspection

This is general safety information, not a substitute for emergency services. If you smell gas, get out and call 911. Learn more at our FAQ page.

Frequently Asked Questions

What should I do if I smell gas in my home?

Leave immediately with everyone, don't touch electrical switches or use your phone inside, then call 911 and your gas utility from outside. Don't re-enter until professionals confirm it's safe.

Why does natural gas smell like rotten eggs?

Natural gas is odorless, so utilities add a sulfur-based odorant deliberately so leaks can be detected. Never brush it off.

How can I tell if my furnace is leaking carbon monoxide?

Warning signs include a yellow rather than steady blue burner flame, soot around the unit, and flu-like symptoms without a fever — especially if several people or pets feel sick at once. Working CO detectors are your real protection.

Where should carbon monoxide detectors be installed?

On every level of the home and near sleeping areas, tested monthly — required for any Northern Virginia home with fuel-burning appliances.

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