Accuracy Check(1):
A quantitative function check using a known concentration of gas that is traceable to a recognized standard to confirm that the alarms are functional and that the sensor(s) response is within acceptable limits. Typically, a +/-10% to +/-20% of applied gas value is considered acceptable unless otherwise specified by the manufacturer, internal company policy, or a regulatory agency.
Bump Test Function Check(1):
A qualitative function check where a challenge gas is passed over the sensor(s) at a concentration and exposure time sufficient to activate all alarm indicators to a minimum of their lower alarm setting. The purpose of this check is not to confirm the accuracy of sensor response, just that gas can get to the sensor(s) and that all the alarms present are functional.
Span calibration(1):
The adjustment of the sensor(s) response to match the value of a known concentration of applied gas that is traceable to a recognized standard. The calibration procedure should be done in accordance with the equipment manufacturer’s instructions.
Zero calibration(1):
Establishes sensor(s) baseline reading, 20.9% oxygen and free of any toxic or combustible gas vapors. To maintain a stable baseline, it is essential to perform zero calibration in fresh air. In the event, fresh air cannot be confirmed, use zero grade air or N2 to perform a detector zero calibration. Perform a zero calibration to reestablish baseline as required, and before a span calibration.
References Sources:
(1) Honeywell Analytics - Gas and Flame Detection Bulletin Number: 2017115-2 19/06/2018