For nearly a year, the Hernandez family had no idea it was being poisoned.
Even a visit to the hospital couldn't pinpoint the source of the headaches, nausea and confusion plaguing the Daly City family. It wasn't until February, when a PG&E inspector took a look at their furnace, that the family members discovered the cause of their ailments.
The culprit? Carbon monoxide, an odorless and colorless gas produced in the combustion of fossil fuels - like in the furnace in the Hernandezes' apartment. In high enough doses, it can be lethal.
Beginning July 1, a state law will require carbon monoxide detectors in all single-family homes to prevent such potential tragedies, making California the 35th state to enact some sort of carbon monoxide legislation.
To meet the new standards, homeowners must install carbon monoxide alarms, which look like smoke detectors, on each level of their home. Ideally, the alarms should be near carbon monoxide-emitting appliances - gas-burning stoves and heaters, for example - and near sleeping areas.
Apartment rule in 2013
Newly constructed residences have been required to have the detectors since January. All other types of residences, like apartment buildings and multifamily homes, will be required to install carbon monoxide alarms by Jan. 1, 2013.
Failure to meet the standards will be punishable by a fine up to $200 for each offense. While homeowners will not be subject to inspections to ensure compliance with the law, they will be held to the code during the building permit approval process or when selling their home - much like the current policy on smoke alarms.
"Hopefully, people will get the idea that this is for your own safety and your family's safety," said San Francisco Fire Department spokeswoman Mindy Talmadge. "It wouldn't be recommended if it wasn't something we thought was necessary and important."
Doctors told Jose Hernandez, 50, who has a wife and two daughters, that it was a miracle the family had survived the high levels of carbon monoxide in their bodies. Every year, between 30 and 40 California residents aren't so lucky.
Difficult to detect
One of the principal dangers of carbon monoxide is that, without detectors, it is nearly untraceable.
The American Medical Association estimates that 20,000 emergency room visits nationwide result from carbon monoxide poisoning annually, and it is the leading cause of accidental poisoning deaths in the country.
An additional complication comes from the fact that early signs of carbon monoxide poisoning, which include nausea, dizziness and fatigue, are easily misdiagnosed as symptoms of the flu. Talmadge believes that cases of carbon monoxide poisoning are underreported.
Because of the health risks, Talmadge says, it is important that carbon monoxide leaks are detected early.
"The ideal situation is that it's detected before you start experiencing symptoms," Talmadge said. "Once you do, there's carbon monoxide poisoning in your system. If it occurs at night while people are sleeping, it's kind of a silent killer."
Carbon monoxide poisoning is more common during the winter, when more homes use gas heaters - one of the most common household sources of carbon monoxide.
According to state Sen. Alan Lowenthal, D-Long Beach, the author of the bill that established the new regulations, California's milder climate is one of the reasons legislation has come later here than in other parts of the country, where states see a dramatic increase in poisonings during the winter months.
While earlier versions of the bill raised questions about the availability and quality of carbon monoxide detectors, they are now inexpensive and far more reliable than they were five years ago.
Carbon monoxide detectors can be purchased at most hardware stores. Basic models cost around $20. The detectors come in battery-powered and plug-in versions. Homeowners are advised to purchase detectors with battery backup in case of a power failure.
Although the Ace Hardware on California Street in San Francisco has seen a small uptick in sales of carbon monoxide detectors, store manager Josh Weinberg says he is surprised it hasn't been greater.
"We're not seeing the onslaught one would expect when a new law is publicized, but I'm doing what I can," said Weinberg, who has put up a display and posted the new regulations in his store.
Hernandez, whose landlord has now equipped the whole building with carbon monoxide detectors, thinks the new legislation is "a great idea."
"Every family should have them," he said.