It’s relatively cheap.

It’s more convenient than traditional pipe rehabilitation projects.

And it’s already been used to repair hundreds of millions of miles of underground infrastructure in the United States alone.

Cured-in-place pipe lining is an increasingly popular method of repairing old and damaged sewer and stormwater pipes without having to dig up streets, reroute traffic or haul away debris.

But there’s a catch: Noxious fumes created during the process can escape the job site and sicken people in their homes, schools and businesses.

Here are five key takeaways from our recent investigation into the cured-in-place pipe industry that you need to know.

Read the full investigation:A popular, but noxious, piping fix is sickening people. It’s throughout America’s sewers.

How the CIPP process works

Cured-in-place pipe lining creates a new pipe inside an old one when workers insert a soft, resin-soaked liner into a damaged pipe, inflate it with pressurized air, then heat it with steam, hot water or UV light so it hardens.

During the heating process, volatile organic compounds in the resin mixture are released as a chemical plume that can escape from manholes and travel through the lateral connections linking the main pipe to the properties it serves.

Plumbing fixtures called P-traps are supposed to block these fumes from entering a building through sinks, toilets and drains. But they’re not a failsafe. The emissions can also seep through cracks in the foundation, doors, windows and air intakes.

Learn more about how CIPP works:

People exposed to these fumes have described an odor similar to that of epoxy or model airplane glue. Many said it irritates their eyes and throats. Some have experienced nosebleeds. Other common complaints include dizziness, headaches, slowed reaction times, loss of balance, nausea and unconsciousness.

Dozens of incidents from coast to coast have landed people in the hospital, triggered evacuations and sparked lawsuits claiming injuries and even death.