The TR-6600 prefilter can extend the service life of the particulate (HE) element of TR-600 series filters and cartridges by capturing large particles that may otherwise clog the HE filter. Frequent prefilter changeout may help optimize PAPR system performance.The TR 6600 prefilter can extend the service life of the particulate (HE) element of TR 600 series filters and cartridges by capturing large particles that may otherwise clog the HE filter. Frequent prefilter changeout may help optimize PAPR system performance. The TR 6600 prefilter must be installed and used according the the User Instructions. Use of the TR 6600 may reduce PAPR operating costs by extending the service life of the main filter/cartridge. The TR 6600 is maintenance free and should be discarded when loaded or damaged.