Greenville, SC – The silent killer had already begun to attack. There were warning signs, but Sandy Halkett didn’t recognize them.

Her husband was traveling out of state as she prepared to shuttle three children off to school when a piercing alarm beeped at 6 a.m. last Wednesday.

The carbon monoxide detector hanging in her home showed a reading of 188 parts per million as it blared. Nine parts is cause for concern, enough to warrant action according to the Environmental Protection Agency.

Sustained exposure to the levels the family was absorbing could’ve killed Halkett and her children.

But they were saved by a device that costs less than $100.

Safety and utility officials say every household should have one.

And Halkett says she now feels it is her intended purpose to spread the word.

“This Thanksgiving we’re really thankful,” she said. “When you have a close call, you go, ‘Wow.’ You’re just happy to be here. It’s not about the turkey. It’s about just being here and having one more day.”

A faulty gas-powered heating unit was to blame for the scare. Cracks in the exchange caused carbon monoxide that would normally dissipate into the atmosphere to be sucked into their home on Pinewood Drive in Greer.

Halkett doesn’t know how long it had been going on. The family had only recently begun using their heater this year. They’d noticed climbing readings on the carbon monoxide detector but thought nothing of it since its alarm hadn’t sounded, yet.

Sandy, her husband Scott and their children had experienced dry mouth and slight headaches. Once Scott felt nauseas suddenly without apparent reason.

Those were red flags that there was a problem, but they went unnoticed because they were common and minor. The colorless, odorless, tasteless gas was far from apparent.

The carbon monoxide detector provided a safety net.

Luke, 10, Campbell, 9, and Gabriel Halkett, 7, were rattled by its commotion when it sounded before Sandy sprang into action.

“I said, ‘Let’s just get dressed. We’re all OK. We’re going to be fine. Let’s go to school,'” Halkett said. “They said, ‘What are you going to do, Mommy?’ I said, ‘I’m going to call the fire department when you go to school.’ They said, ‘Ooh, take a picture of the fire truck.'”

The Greer Fire Department arrived for more than a photo opportunity. Their detectors confirmed the contamination.

A technician from the Greer Commission of Public Works arrived to turn off the gas supply to the house.

The supply wasn’t restarted until the Halkett family had a new heating unit installed and the threat was confirmed to have been eliminated Saturday night.

They no longer had to bundle up in their cold living room. They no longer had to shower at a neighbor’s house. And they no longer had to breathe unhealthy levels of carbon monoxide.

The fire department and CPW get calls like Halkett’s from time to time. Carbon monoxide poisoning is a serious threat. Nearly 200 Americans die annually from accidental carbon monoxide poisoning, according to the Centers for Disease Control and Prevention.

For healthy adults carbon monoxide becomes toxic when it reaches a level higher than 35 parts per million with continuous exposure over eight hours. Levels of at least 200 parts can produce dizziness, drowsiness and vomiting in as little as one hour. It can lead to tissue damage and permanent neurological dysfunctions, and it can ultimately lead to death. It accumulates and interferes with the body’s ability to use oxygen.

“You can have it from people parking cars in garages and going out to crank them in cold weather with the door down,” said CPW gas operations manager Rob Rhodes. “You also have it from generators in the wintertime, where they might be up under a floor or in a garage, and from wood burners with the flue or chimney being stopped up.”

“With any kind of combustion process, carbon monoxide is going to be put out, even with oil heaters or kerosene portable heaters, even with electric heat to a certain extent,” said Greer Fire Chief Chris Harvey. “Sometimes change in barometric pressures will set one off, but it’s better to be safe than sorry any day of the week. It doesn’t cost anything for the fire department to come out and check it.”

As Sandy Halkett reminds folks these days – from friends to students she teaches golf to at Eagle Zone – failure to act could cost everything. She said one of the men who gave her an estimate for her new heating unit told a story of a cousin who survived two tours in Vietnam only to die in his recliner of accidental carbon monoxide poisoning.

“At first I was just like, ‘OK, we’re here.’ Then it’s, ‘Could we have died? Am I overreacting about this? Am I overplaying this?'” Halkett said. “Stories started coming in on my Facebook page of people who didn’t make it or where somebody in the house made it and somebody didn’t. I realized we were lucky.”