A: A bump test is a functional test of a gas monitor. Sensors and alarm indicators are tested, ensuring acceptable performance of sensors and monitor before use. All sensors are challenged with a known quantity of gas, and instrument response is compared to the actual quantity of gas present.
OSHA says, "The International Safety Equipment Association (ISEA), founded in 1933, is a trade association for manufacturers of protective equipment, including environmental monitoring instruments. The ISEA recommends, at a minimum, verification of sensor accuracy before each day's use.
The only way to guarantee that an instrument will detect gas accurately and reliably is to test it with a known concentration of gas. Exposing the instrument to a known concentration of test gas will show whether the sensors respond accurately and whether the instrument alarms function properly. A bump test verifies calibration by exposing the instrument to a known concentration of test gas.
The instrument reading is compared to the actual quantity of gas present (as indicated on the cylinder). If the instrument's response is within an acceptable tolerance range of the actual concentration, then its calibration is verified.
Sensors, especially LEL (combustible) sensors, may be lose sensitivity to the target gas through poisoning. Silicone compounds including silanes, halogens, halogenated hydrocarbons, sulfur compounds, as well as acids and bases and various VOCs are known poisons.
The only way means of identifying loss of sensor sensitivity is by gas-checking or calibration. As a result, CSA, UL, OSHA and instrument manufacturers require a bump test before every day's use.
Click HERE to view a document on Bump Test.
Click HERE to view a document on Measuring VOCs.