In 2008, during the coldest winter in decades, a Utah family faced a "perfect storm."
Snow was piling up on the roof of their manufactured home, their tiny infant was sickly and church members were buzzing about the possibility of child abuse.
By spring, the couple -- Mary and David Conrad, who as practicing vegans ate no meat products -- were charged by state welfare authorities with the nutritional and medical neglect of their baby Daniel.
"When you saw this child, he looked like he was on death's door, he was so green," said Clint Greenhalgh, 46, and a neighbor in the couple's low-income town of Manti.
But the Conrads were quickly convinced by a scientist friend, Thomas L Rodgers, that something else was sickening Daniel.
They blamed a precarious set of events -- cold weather, unrelenting snow and government regulations that allow the furnace vents in their manufactured home to be placed only three feet apart.
They say Daniel, now a healthy 16-month-old, was poisoned by carbon monoxide, also known as "the silent killer," which they believe was sucked into their house through a fresh-air vent.
For the next eight months, the Conrads, who have four other children age 6 to 16, waged a successful battle against Utah's Division of Child and Family Services and the courts to keep Daniel.
Today, they are warning other families of the dangers of low-level carbon monoxide poisoning, especially in factory-built homes.
"Mobile homes have stubby little vents and the snow cover adds to the risk," said Thomas Greiner, associate professor of engineering at Iowa State University. "You get cold weather and a potential for snow buildup that blocks the intake and exhaust."
"I have seen it happen in other types of furnaces and with short vents on flat roofs," he told ABCNews.com. "In several cases we had people almost die. One went to the hospital three times with undiagnosed problems."
There will never be conclusive proof that Daniel was poisoned by lethal exhaust fumes, but his curious case illustrates the difficulty in deciding when to test for carbon monoxide poisoning, which brings between 15,000 and 40,000 Americans a year into emergency rooms, according to the Centers for Disease Control and Prevention.
In the Conrads' case, the problem was visible, according to one witness, former state senator and heating specialist Parley Hellewell.
"When it was cold, you could see the exhaust come out of one [vent] and go down the other," he told ABCNews.com.
Hellewell and Rodgers had intervened in a similar Utah case in 2005. A family was charged with child abuse when one baby died and another appeared malnourished. The family was vindicated when experts found the furnace exhaust and an old air vent were only 11 inches apart, causing carbon monoxide to poison the entire family.
"It's definitely a hidden hazard and something needs to be done about it," he told ABCNews.com.
The Conrads' story has caught the attention of local media, state legislators, the Sierra Club and now, the Department of Housing and Urban Development, which regulates the design of manufactured homes.
The family wants local and state codes -- which require the vents to be at least 10 feet apart, much stricter than HUD's code -- to be enforced in manufactured homes. And, because Daniel was never tested, they want to require hospitals to routinely administer a simple blood test to detect carbon monoxide poisoning.