This red light goes on when air purifier needs to be cleaned, also check out whether fan is running or fan is stopped if fan is not running and red light is on then the problem is of filter got wet inside.let the filter get dry then check out.if still the same problem the filter needs replacement. to remove the filter for cleaning or replacement Remove the ESP cell by taking hold of the handles and lifting upwards. and then Remove the Oxygen Plus filter from the unit.by lifting it up slightly. its the filter problem either its wet and needs to be dried out or the filter is got clogged by dust and needs replacement.contact the local service center for air purifier and get the replacement filter.------ This will help. Thanks please keep updated.please do rate the solution positively .thank you for using fixya.