Is your machine too loud or running slower? Your PSA Nitrogen generator (NTF-8 and Nitrofill E-170, NCS Green Machine) use a solenoid muffler designed to lower the decibels of the solenoid's purge cycle. Over time these mufflers become clogged with carbon dust thus slowing down the machine and reducing Nitrogen purity. We recommend changing these mufflers out once a year. Set of 2 mufflers with connection fitting.