Every manufacturer recommends a bump-test before each days use, meaning if you are planning on using your meter, it must be bump tested before using it that day. A bump test is nothing more than applying a concentration of known gas in “normal running” mode to verify sensor response and alarms.
Note: Do NOT apply a high concentration of gas (CO- Engine Exhaust or Flammable Gas) as this will overdose the sensor and could lead to early sensor replacement.