ORANGE >> Fourth-grade teacher Teri Alves, who survived the mass shooting at Sandy Hook Elementary School, tooled part of her recovery by inventing the Yogi Wrap, designed to keep yogurt and other lunchbox items cold for 10 hours.

Alves, now a teacher at Race Brook School, was one of the first to dial 911 on that day survivors refers to as “12/14/12.”

The horror when gunman Adam Lanza killed 20 children and six adults will never leave Alves.

But through therapy for post-traumatic stress disorder, she learned about “post-traumatic growth,” and while on maternity leave soon after the shooting, she resumed working on an idea for a product she began in summer 2012.

“It took over the place of trauma,” she said. “Without the PTSD, I wouldn’t have had the drive.”

Alves started the project because her oldest daughter, Avery, now 6, was in a room at day care where the children could not refrigerate lunch.

Avery liked her yogurt really cold, but Alves couldn’t find a perfect lunchbox ice pack that kept it cold enough for long enough.

After a lot of shopping, Alves thought, “There should be one that wraps around yogurt.”

She began experimenting at home with duct tape, plastic wrap, dimensions.

She put the project aside, as the school year was about to resume.

Then, just a few months later, the shooting happened.

Eight and a half months pregnant with a second daughter, Alves was teaching in her third-grade classroom in the back of the school building, when the gunman shot through the front entrance.

Alves remembers a loud noise, which she thought were stacks of metal chairs falling, she said.

She looked out her door and saw the custodian bolting to the front of the school, and when the noise became clearer, she recognized it as gunfire.

After seeing the way the custodian moved, and identifying the sound, Alves knew there was a shooter in the building.

She  got the classroom key , locked the door, drew the blinds and put the kids into the lockdown mode they had practiced many times.

Alves reassured the kids that everything was going to be OK, but then the public address system was triggered and the sound of bullets, sirens, adult dialogue and swearing was loud and clear, she said.

She also heard people on the roof, and feared it was another shooter, but it turned out to be police.

There were four minutes of shooting, but it felt like a half hour, Alves said. After it was over, police knocked on her door, but she wouldn’t open it because she had been trained to wait until they showed identification.

When she realized there was a sea of police officers, a very pregnant Alves bolted with her class out the back door, and was implored to slow down.

Later that night, she went into premature labor. She remembers telling her husband, Carlos, that she didn’t want their daughter, Adrian, now 3, born on that day.

Doctors managed to stall the delivery and soon she was back at work with the others in a temporary school with her Sandy Hook School community, brought closer through the tragedy.

Three weeks after resuming school she went out on maternity leave and that is when she picked up the ice pack project again, this time going full on to help channel the emotional pain.

In addition to doing Bikram Yoga and resuming her running, Alves began working on prototypes for what would become the Yogi Wrap. She reached out to various companies to “pick their brains,” and found a great sourcing agent, someone who brings a product idea to manufacturing.

The Yogi Wrap is an ice pack of extra-coldness that becomes a cube with the help of Velcro tabs to encase the yogurt or other product, keeping it cold on all sides. It can also hold fruit cups, juice boxes, applesauce squeeze containers and combinations of items. The product inside the ice pack increases coldness.

Alves holds a provisional patent, and the product, available since April, is sold at Yogiwrapshop.com for $5.99. She has already sold 500 without much advertising and is hoping to get Yogi Wrap into the retail market.

A twin, who grew up in Fairfield, she taught at Sandy Hook School for 12 years until ► moving to Orange from Shelton in 2015 and ◄ being hired at Race Brook School.

“When I was doing this idea and I was at Sandy Hook, I thought: ‘This is my ticket out (of teaching),’” she said.

But now that she’s in Orange, away from the memories, Alves said she sees the wrap just as extra income.

Although the shooting brought the Sandy Hook crew closer — they spent a lot of time together afterward — leaving and teaching in Orange was “refreshing,” and the best thing she could have done, Alves said.

“They were the ones I was closest with. We could say stuff to each other that you wouldn’t say out loud,” she said. She estimates 80 percent of the staff remained at Sandy Hook after the shooting.

But still, Alves said, “A big part of me is at Sandy Hook.”

Since the shooting, Alves said she is a changed person.

Although “not a tattoo type,” she now has a tattoo of a dove on her wrist.

“To me, it represents flight and moving forward. The hope of peace and all that doves stand for,” Alves said. The dove has a green eye because that is Sandy Hook Elementary’s school color.

Alves also has a tattoo of hearts on her ankle to represent her daughters, husband and twin sister.

She’s had a lot of therapy for the PTSD and has worked hard to turn that into the post-traumatic growth that fueled Yogi Wrap. She said teachers were allowed to leave during the school day for therapy following the shooting.

Alves said now she’s a lot more of a black and white thinker. “You just prioritize things a lot better. What’s important, what’s not important,” Alves said.

She said that like everyone, teachers have their gripes, including about situations like broken copy machines, but since that day she’s realized “a lot of stuff doesn’t matter.”

Alves lost two close friends in the shooting: teacher’s aide Ann Marie Murphy, 52, who had worked in her class two years and died protecting her student, and school psychologist Mary Sherlach, 56. Another victim, teacher Victoria Leigh Soto, 27, covered Alves’ class during her first maternity leave.

Even today, nearly four years later, a half day doesn’t go by when she doesn’t think about the shooting, Alves said.

The students were traumatized along with staff and were triggered by everyday noises or smells that reminded them of that day. They regrouped when noises and smells were explained with reason, she said.

Although she’s made vast improvement, Alves still struggles with triggers. She’s only been to two movies since that day because she didn’t want to be in public in the dark.

Alves also couldn’t stand the sound of fireworks after the shooting and feared for her children’s safety to an extreme degree.

“It was emotionally difficult leaving Sandy Hook, but I don’t regret it,” Alves said, noting there was “guilt” in leaving. “I’m a better mom, teacher and wife.”