Crowcon T4-EXT-F is an external clip-on filter plate for use with Crowcon T4 portable multigas detectors in dusty environments. The filter plate will protect the sensors, making it easier to maintain T4. It is suitable for use in a hazardous area. It has been designed to operate with the charging accessories and does not need to be removed when inserting T4 into the desktop charger ( 122-5521 ), the 10-way charger ( 122-5527 ) or the T4 vehicle charger ( 122-5528 ).