Gas monitors are sophisticated instruments, but changing sensors is easy. By taking your time and following these simple instructions for replacing sensors, your BW Honeywell monitor will be back in the field in no time. Remember, new sensors require a few hours to burn in - especially the O2 sensor - so don't turn the monitor on right away. Once you restart the monitor, you may receive a "sensor fail" message. Check through your work to make sure you installed the new sensors all the way. If the problem persists, call BW Tech Support at 1-888-749-8878.