Two people from Falmouth have been taken to hospital after accidentally mixing chemicals and inhaling the fumes.
Paramedics treated them at the scene before transferring them to the Royal Cornwall Hospital in Truro for further examination.
Firefighters entered the property to find the chemicals, before removing them and ventilating the home. They established the gas inhaled was chlorine.
Cornwall Fire and Rescue say they were called to the incident at 15:00, and sent crews from Falmouth and Tolvaddon.
A support vehicle from St Just and the environment support vehicle from Penzance was also called out.