Your EtO monitoring system is very sensitive, and must respond to sub parts-per-million (ppm) concentrations of this gas. It may be that maintenance crews are using floor wax, strippers, assorted cleaning products, or isopropyl alcohol, and these compounds can cause a response on the system, especially since they would be present at concentrations in excess of 500 ppm.
The sampling pump(s) of the system should be shut down temporarily during these maintenance operations, to avoid false alarms. A special timer, that re-starts the sampling pump(s) after a customer-adjustable time interval, is available to perform this action automatically.
Do not attempt to remove these interferences by covering the sample inlet with a rag or other obstruction, as this can clog up the sample inlet, thus causing the pump to pull its full vacuum on the sensor—leading to irreversible sensor damage.