The Hastings mass flow meter (HFM-D-301/305) and controllers (HFC-D-303/307) are intrinsically linear and are designed to accurately measure and control mass flow over the range of 5 sccm to 2500 slm. Hastings mass flow instruments do not require any periodic maintenance under normal operating conditions with clean gases. No damage will occur from the use of moderate overpressures (~500 psi/3.45MPa) or overflows. Instruments are normally calibrated with the appropriate standard calibration gas (nitrogen) then a conversion factor is used to adjust the output for the intended gas. Calibrations for other gases, such as oxygen, helium and argon, are available through special order.