Third-party calibrators

It is possible to calibrate Aeroqual gas modules using gas dilution calibrators from other suppliers such as Teledyne (shown), Thermo Fisher or Ecotech (also shown):

They aren’t as portable as the Aeroqual AirCal 1000, but some do include an ozone generator and have the ability to perform gas phase titrations (GTP).

• If the calibration cylinder is in a balance of nitrogen, the minimum dilution amount must be 50 x dilution.
• If the calibration cylinder is in a balance of air, there’s no minimum dilution.
• The final span concentration delivered must be in the range specified in the Recommended cylinder concentration document below. For example, for CO, the concentration must be between 5 and 15 ppm, which means the dilution range of the calibration system must be considered and the concentration of the gas cylinder must be matched to the range of the calibration system.

For recommended gas cylinder concentrations for span calibration, see here.

A dilution calibrator with a built-in O₃ source allows a gas phase titration of NO to NO₂. The advantage of this method of generating NO₂ is that it enables the use of the more stable NO gas for NO₂ sensor calibrations. The AirCal 1000 doesn’t have this facility. If you plan to use a calibrator with GPT capability, you should only use a small excess of O₃ (<0.025 ppm) because excessive O₃ may adversely affect the NO₂ calibration.

Alternatively, use an excess of NO to enable a NOx calibration simultaneously. For example, a setting of 0.2 NO and 0.1 O₃ would produce 0.1 ppm NO₂ and 0.2 ppm NOx.

Aeroqual’s gas sensor calibration can be adversely affected by the very dry (dew point < -20^oC ) air generated by third-party calibrators.

If you’re using a third-party calibrator with a dry zero air source or a cylinder of zero air, you’ll need to humidify the calibration gases before they’re delivered to your Aeroqual monitor.  Aeroqual supplies a calibration humidifier as part of the AQM 65 service kit. It contains a nafion membrane from Permapure, which allows the transport of water molecules across the membrane with high selectivity and no loss of calibration gases.

The humidifier is placed between the outlet of the calibrator and the inlet of the monitor. The tee on the gas inlet must be open to allow excess gas to vent.

Note: If you’re using an AirCal 8000 or an AirCal 1000, you don’t need to use a calibration humidifier to calibrate Aeroqual gas modules. These calibrators are specially designed to optimally prepare the calibration gases for this monitor.