All gas detectors must be calibrated on a schedule. Of the two types of gas detectors, portables must be calibrated more frequently due to the regular changes in environment they experience. A typical calibration schedule for a fixed system may be quarterly, bi-annually or even annually with some of the more robust units. A typical calibration schedule for a portable gas detector is a daily bump test accompanied by a monthly calibration. Almost every portable gas detector out there has a specific calibration gas requirement which is available from our company.