A new study led by researchers at Georgia State University finds a large majority of e-cigarette users are modifying their devices-often in dangerous ways.

The study, led by Associate GSU Professor Lucy Popova, indicates users make changes to their devices that can result in harm.

“Changes to e-cigarettes that the manufacturers actually plan for, like replacing a coil that is designed to be replaced, and also modifications that are not designed, like adding a different substance to e-liquid,” Popova says.

She says education is key and urges those who put information online to include warnings about these modifications.

“Whenever you change the voltage of wattage, the coil can heat up higher, and the higher you will heat something, the e-liquid, the more harmful chemicals release into the aerosol,” Popova warns.