What Does It Mean When a Furnace Is Red-Tagged?

A red tag on your furnace means someone qualified, either the gas utility or a heating technician, found a condition they judged unsafe, shut off the gas to the furnace, and tagged it so nobody turns it back on. It stays off until the problem is repaired or the furnace is replaced and a technician clears it to run.

The tag is a written record: who found the problem, what they found, and when. It isn't a fine or a city order. The shutoff is there because the condition can put carbon monoxide or raw gas into the house, and it's the one furnace problem you shouldn't try to work around, even on a cold night.

Who can red-tag a furnace in the Twin Cities?

Two groups do most of the tagging in the Twin Cities:

• The gas utility. CenterPoint Energy supplies gas to Minneapolis and much of the metro, and Xcel Energy supplies gas in Saint Paul. Utility crews tag appliances when they respond to a gas odor call, a carbon monoxide call or a service restart and find something unsafe.
• A heating technician. During a repair or tune-up, a technician who finds an unsafe condition shuts the gas off to the appliance and tags it.

Either way, you should get an explanation and, ideally, something you can see: a photo or video of the crack, the carbon monoxide readings, or the gas leak marked with soap bubbles.

Why do furnaces get red-tagged?

Cracks and CO are covered in more depth in our posts on cracked heat exchanger symptoms and whether a furnace can leak carbon monoxide.

In older Minneapolis and Saint Paul houses, venting shows up a lot. The furnace and water heater often share a brick chimney, and the metal connector pipe between them and the chimney rusts at the joints after decades of Minnesota winters. On newer high-efficiency furnaces, snow drifted over the PVC pipes is a common cause of a furnace shutting itself down, but that's usually cleared on the spot rather than tagged. Our guide to clearing a frozen furnace vent shows how to handle it safely.

What should you not do after a furnace is red-tagged?

• Don't relight the furnace or turn its gas valve back on.
• Don't remove the tag or ask someone to "just get it through the night."
• Don't bypass a switch, jumper a control or reset a rollout switch to get heat back.
• Don't heat the house with a gas range, oven, grill or generator. CenterPoint Energy warns that running a range for heat can produce dangerous levels of carbon monoxide, and Xcel Energy says never to use outdoor barbecues, kerosene heaters or camping heaters indoors.

If you smell gas at any point, leave the house without flipping switches and call 911 from outside, then call the utility. Both Xcel Energy and CenterPoint Energy give that order: get out, call 911, then call them. Make sure your carbon monoxide alarms work, too. Minnesota law requires one within 10 feet of every sleeping room, and our CO alarm placement guide shows where they go.

Getting through a cold night

A red tag in January is a planning problem. Xcel Energy says indoor electric heaters are safe when used properly and suggests closing blinds and drapes and keeping doors shut to hold heat. Plug space heaters straight into a wall outlet, keep three feet of clear space around them, and don't run several on one circuit. Open the sink cabinets on outside walls and let a faucet drip if the house cools fast. Xcel also suggests staying with family, friends or at a hotel if you can't keep the house warm overnight. Our no-heat checklist covers the rest.

What happens next

1. Get the details. Ask what failed, where, and what the readings were. Write down the furnace's model and serial number from the rating plate so warranty coverage can be checked.
2. Get a second opinion if you're unsure. CenterPoint Energy's own scam warnings describe people who claim a cracked heat exchanger and red-tag working equipment to pressure a quick sale. Its advice: get a second opinion from a licensed professional, verify anyone claiming to be from the utility before letting them in, and check the equipment's warranty status before authorizing work. A good company won't object to a second look. Keep the furnace off while you wait.
3. Choose repair or replacement. Get both prices in writing.
4. Have it retested. After the fix, the technician should run the furnace, check combustion and carbon monoxide, and confirm the venting drafts properly before clearing it.

What does it cost to fix a red-tagged furnace?

National cost guides give a sense of scale. HomeGuide puts a heat exchanger replacement at a typical national range of $1,000–$3,000, a gas valve at $200–$800 and an inducer motor at $400–$1,100. A new heat exchanger makes the most sense on a younger furnace whose manufacturer's parts warranty still covers it, so you're mostly paying labor. On a furnace past about 15 years, replacement usually wins.

A new furnace with us runs $4,500–$9,500 installed: roughly $4,500–$6,000 for an 80% AFUE model and $6,500–$9,500 for a 96–98% model. It comes with a 2-year labor warranty on top of the manufacturer's parts warranty, sized with a Manual J load calculation. Our furnace replacement cost guide explains what moves the price, and our guide to choosing an HVAC contractor covers what to check before you sign.

Getting a red-tagged furnace looked at

If your furnace was red-tagged, by us or anyone else, we'll inspect it, show you what we find and give you a written, flat-rate price before any work starts. A furnace repair visit is a $79 trip charge, waived when you approve the repair, and the same pricing covers furnace repair in Minneapolis and furnace repair in Saint Paul. We're open 7 days, 7am–9pm, and no-heat calls go to the front of the schedule. Call 612-429-3465.

Questions

Sources

• Xcel Energy mn.my.xcelenergy.com
• HomeGuide cost guides (2026 editions) homeguide.com