Armed with two garden hoses connected to a bursting faucet, Matthew Craig battled fire and smoke to save his house from the onslaught of flames that ravaged much of Altadena, a once-green corner of Los Angeles County. The wind was like a dragon’s breath, he said, and “we all ate smoke.”

But while his home is safe, for now it will be a long time before he and his family feel safe enough to return. Every room in the house, he said, was covered in ash, dust, soot and dirt that the high winds had blown inside. “My 5-year-old son, wife, dog and I do not want to live in a toxic wasteland.”

As residents begin to return to fire-ravaged neighborhoods, they are grappling with a host of toxic hazards in lingering smoke and ash that experts say can cause breathing problems and worse.

When neighborhoods get smoky, a variety of man-made materials—vehicles, lead pipes, paint, plastics—are ignited, which can release toxic smoke and vapors that can linger. A recent study found that even for homes that are spared destruction, smoke and ash brought inside can stick to rugs, sofas and drywall, creating health hazards which can stay for months.

“There are so many people who have lost their homes in this, and it’s devastating,” said Colleen Reid, who studies the health effects of air pollution at the University of Colorado Boulder and who led the research. “But even people who feel lucky that their home is OK – they could actually be exposed to a lot of toxic materials,” she said. “Wind will come through every crack.”

This was a particular problem, Professor Reid said, because some people were more likely to return more quickly or deal with the clean-up themselves if their insurance companies did not cover this type of damage from ash and soot. And sifting through the ash could send dangerous particles back into the air. There have been moves in some states to try to force more insurance companies to cover smoke and ash penetration, she said.

Smoke and overall air quality it still poses a risk, said Yifang Zhu, a professor of environmental health at the University of California, Los Angeles. Soot and other fine particles, known as PM2.5, can penetrate the lungs and heart and even enter the bloodstream, affecting the entire body.

Ironically, weakening Santa Ana winds that could help firefighting efforts also meant more smoke would stick around, she said. And the air quality readings, which focus on particulate pollution like soot, also weren’t a good indicator of other complex air pollution hazards the fires caused, she said.

Typically air quality index it does not capture volatile organic compounds, for example, which can cause headaches and nausea and are linked to cancer and other diseases in the long term. And N-95 masks are not as effective against those other pollutants.

“There were so many things that burned and so many other air toxics,” she said. “That’s why you can feel something, even if the air measuring devices don’t pick it up.”

For people returning to homes in affected neighborhoods, there are steps they can take to protect themselves, she said. Respirators with a carbon cartridge work better against toxic air pollution than masks. Children and the elderly, as well as people who are pregnant or have asthma or underlying respiratory or heart diseases, should not participate in the cleaning.

Seek medical attention for any serious symptoms that occur – chest pain, wheezing, severe cough – and avoid strenuous exercise. Where possible, stay indoors and turn on air purifiers equipped with activated carbon filters, in addition to HEPA ones. “It’s just a good idea to be careful,” said Dr. Zhu.