The RKI FP-301 is a high-sensitivity version of the FP-300 paper-tape monitor, using a dedicated chemcassette tape tuned specifically for arsine and hydrogen selenide rather than a general-purpose formulation — giving roughly 10x finer resolution than the standard FP-300 arsine tape. A digital LCD reports concentration in ppb or ppm, and an internal sample pump feeds air continuously across the tape for real-time monitoring.

Latched common relay contacts cover warning, alarm, and trouble conditions alongside a 4-20mA output, and the FP-301 is available in panel-mount (24VDC, ~14.3 lb) or desktop (100-220VAC, ~12.1 lb) configurations — built for uncaptured scrubber exhaust and semiconductor fab environmental monitoring where trace-level arsine or H2Se detection matters.