Monitored gases - detect a target gas or hydrolysis byproducts? Suitability -  monitoring location e.g. duct, tool jungle, room air, etc. -  physical constraints e.g. temperature, humidity, RF interference Sensitivity - how repeatable is detection of a specific gas concentration? Stability - how does response degrade with time? Response Time - how fast would it detect a leak? Selectivity - how specific is it to a target gas? Poisoning - loss of sensitivity after exposure to high gas concentration Useful life - how long before sensor cell or electrolyte needs replacement? Maintenance - how often and how long the system would be off-line? Warm-up period - how soon the system would be on-line after maintenance? Ease of calibration - can facility staff be trained or does system need special skills? Smart features - self diagnostics check on circuit and sensor performance Immunity to false alarms - is system shielded and grounded against RFI/EMI interference?