Idaho Mom Warns of Carbon Monoxide Dangers After Her 5 Children and Sister-in-Law Survive Poisoning

An Idaho mom is urging others to install carbon monoxide detectors in their homes after her family nearly died from being poisoned last week.

Ashlyn Hansen tells PEOPLE she feels fortunate that nothing worse happened to her five children and sister-in-law, Heather Hirschi, following their recent exposure to the colorless, odorless gas.

"I'm feeling so incredibly grateful for the fact that I still have all of my kids with me today," Ashlyn, 32, says of daughter Hadlee, 11, and sons Gunner, 10, Gage, 7, Sawyer, 4, Kade, 2, and Crew, 2 weeks.

"With how bad it was, they shouldn't have walked away like they did," she adds. "But I'm so grateful that's how it turned out."

Ashlyn first opened up about the incident in a candid Facebook post on Nov. 9, two days after the scary ordeal began.

"I wasn't going to share this, but I have been letting it all run through my head over and over, all night wondering what I could've done different[ly] or thinking I should've known this is what was happening from the beginning," she wrote. "And the truth is, there was no way of knowing until they were so far into it."

The Rexburg-based mom told East Idaho News that she and her husband Michael Hansen, 33, were in the hospital with Crew on Nov. 7 when they were alerted that Gage wasn't feeling well. At the time, Crew was just four days old and recovering in the cardiac ICU after undergoing open-heart surgery from health complications, the outlet reported.

Meanwhile, the couple's five children were staying at home with Ashlyn's sister-in-law, the mom explained in her post.

"My sister-in-law got to our house to take over babysitting on Sunday afternoon," she wrote. "By that night, Gage said he had a headache and his stomach wasn't feeling good. I told him to take ibuprofen and call me the next day. He called me before school and said the same thing... so I told him he could stay home."

Ashlyn noted to East Idaho News that she had recently received an email from Gage's school "that said COVID, cold, and flu was going around."

"I chalked it up to one of those and thought that he might just be feeling a little bit off," she said.

That same day, Ashlyn learned that Hirschi was also experiencing a headache and nausea. "She figured she'd drink more water and eat something good and she'd feel better," the mom wrote of her sister-in-law on Facebook.

But things continued to get worse when Kade started showing symptoms of an illness.

"Kade was bawling and not acting himself. He was stumbling around and eventually ended up ok the living room floor and passed out," Ashlyn recalled in her post. "Right then, Gage threw up a ton and laid on the kitchen floor. He couldn't even move ... Heather then got sick too."

"Sawyer had been crying and couldn't stop and that wasn't like him either. She even said [our dog] Chewie was barking like crazy and that should've told me something was wrong," she added.

Though Ashlyn initially assumed everyone was suffering from food poisoning, she knew something wasn't right so she asked her mother-in-law, Lori, to stop by and check on the family.

Immediately after arriving, Lori knew what was wrong: the house was experiencing a severe gas leak and the family was showing symptoms of an exposure, according to Ashlyn.

"I was beside myself when I heard that's what was going on. I thought for sure it was just the flu at first because of the symptoms," she tells PEOPLE.

In her post, Ashlyn said, "Lori got everyone out of the house and up to the ER... They sent the fire department over and sure enough, the gas furnace had been leaking. When they respond to these calls, a normal range for them to see is 10-50. Our house was at 600."

"If they would have stayed in that house through the night, there is a possibility that death would have occurred," Madison Fire Department Capt. Sarah Orr noted to East Idaho News. "I took two steps into the home with our gas meter and it read levels of 300 [parts per million] right there at the door. So automatically, we walked out of the house and had to go on air."

"This is a three-story home with a cellar and all of the levels of the house were 600 [parts per million] so this house was full of carbon monoxide," Orr added. "You should have levels of zero."

At the hospital, Ashlyn said doctors determined that Kade's monoxide levels were the highest of her kids, at 39.

"They said had it been any longer and we may not have the good outcome we did," Ashlyn wrote in the post beside photos of her children wearing oxygen masks in the hospital.

Following the incident, the fire department helped fix the gas line, Ashlyn said. Though the house's carbon monoxide levels were at zero later that night, officials advised the family to sleep elsewhere, according to her post.

RELATED VIDEO: Arizona Family of 4 Found Dead in Cabin on New Year's Day From Possible Carbon Monoxide Poisoning

The mom also told East Idaho News that Hirschi and her kids were all put on oxygen for four hours and were later released. They experienced headaches for a few days after their discharge, but have since recovered from the traumatic ordeal.

With everyone home safe, Ashlyn is now using her story to warn others about the dangers of carbon monoxide and the importance of installing a detector in the home.

"I was aware that it was something dangerous, but I didn't know what symptoms to look for," she tells PEOPLE. "We didn't have a detector. It was something I didn't think about until I had a reason to. We are getting one now, and I hope others will take the time and money to get one too."

"They really aren't expensive and it's a small price to pay to save your family," she adds. "We will never be without one again. I'm so glad they were safe and it wasn't too late for us. It could've been a tragic situation and I'm forever grateful we were spared that."