1. Calibration pre-checks

Download the calibration results form at the end of this user guide.

Fill in tables 1, 2 and 3.

These tables record basic details like date and time, site name, engineer's name, and the equipment that will be used during the calibration.

When arriving onsite, it's important to make sure no new emission sources or obstructions have appeared since the last visit.

Inspect the local surroundings and check for local point source emissions such as open fires or exhaust emissions from a newly positioned generator.

Check for obstructions which may affect the measurements, such as a new fence.

Record your observations in table 4 of the calibration form.

Because the AirCal 1000 and Ozone Calibration Source take at least 30 minutes to warm up and become stable, now is a good time to turn both on.

Turn on the AirCal 1000 calibrator and switch on the pump override switch on the back panel.

If you're calibrating ozone, turn on your Ozone Calibration Source and set it to deliver 0.1 ppm ozone. This allows time for the lamp to stabilize at 0.1 ppm.

Fill in table 5 by completing the steps 2,3 and 4 in this user guide.

Put the monitor into service mode.

Check the gas inlet is secure.

Check the particle inlet is secure.

Check the door locks are operational.

This step only applies to AQM 65 monitors.

If calibrating an AQM 65, check the internal temperature has been stable at the correct temperature.

If the internal temperature isn’t correct, you must address this before attempting a calibration.

Measure and record the gas inlet flow rate.

Record the previously measured flow rate. (You should find this in the monitor's journal.)

Open the monitor door and replace the gas inlet filer. Try to minimize the time the door is open so the sensors can quickly re-stabilize.

Measure and record the flow rate again.

If the inlet rate has changed from the previously recorded rate by less than ± 20 %, check the gas connections for obvious leaks, then use the flow adjustment valve to correct the flow. If the adjustment is unsuccessful, go to table 6 in the calibration form.

If the inlet flow has changed from the previously recorded rate by more than ± 20 %, go to table 6.

You only need to complete table 6 if the inlet flow rate was more than ± 20 % of the previously measured rate, or if using the flow adjustment valve to correct the inlet flow didn't work.

One or more modules can fail the flow check, but others can pass. Calibration can continue on modules that pass.

Modules that fail can be removed and checked without affecting the calibration on the remaining modules.

Check the individual gas connections for obvious leaks. If a leak is found, correct it.

Perform a leak check on the sampling manifold. If a leak is found, correct it.

It's important to have a high-quality flowmeter such as the TSI 4040 or the Bios Defender DryCal.

Record the individual flow rates the last time they were measured.

Measure and record today’s individual flow rates. Record the total flow.

For each module, if the flow rate now equals the previously measured flow rate (± 20 % LPM), pass that module. Otherwise fail it.

If no specific module is causing a problem and all module flow rates are low, adjust the flow rate using the bypass valve.

If no specific module is causing a problem and all module flow rates are low, adjust the flow rate using the bypass valve.

Re-measure and record flow rates for each module.

If the flow rate now equals the previously measured flow rate, pass it.

For those modules which don’t have the correct flow rate and can’t be corrected with the bypass valve, perform a leak check or check for blockages.

If the problem can’t be corrected, remove the module and cap off the gas connections. Record fail in the form.

The total flow rate is reduced when a module is removed.

If the door is left open for the purpose of finding a leak or removing a module, the gas modules will become unstable and you'll need to wait 1 – 2 hours to allow the sensors to re-stabilize.