Direct Reading Particle Counters: Calibration Verification and Multiple Instrument Agreement via Bump Testing

Area of Science:

• Environmental Science
• Analytical Chemistry
• Instrument Calibration

Background:

• Direct reading instruments, such as condensation particle counters, are crucial for monitoring particle concentrations.
• Annual manufacturer recalibration revealed frequent out-of-tolerance readings for two condensation particle counters.
• Reliance solely on annual calibration does not guarantee consistent operational readiness.

Purpose of the Study:

• To evaluate the sufficiency of annual calibration for condensation particle counters.
• To develop and validate a method for confirming instrument operational readiness between calibrations.
• To establish a reliable verification procedure for particle measurement instruments.

Main Methods:

• Analysis of historical calibration records for two condensation particle counters.
• Development of a 'bump testing' method using a reproducible spark igniter particle generation system.
• Establishing a reference response using a newly calibrated instrument and subsequently comparing performance.

Main Results:

• Both examined condensation particle counters spent more time out of tolerance than within tolerance during annual recalibrations.
• The spark igniter system proved reproducible and suitable for calibration verification.
• The developed bump testing method provides a means to confirm instrument performance between scheduled calibrations.

Conclusions:

• Annual calibration alone is inadequate for ensuring reliable instrument performance.
• Bump testing offers a practical and effective solution for verifying condensation particle counter readiness.
• Periodic bump testing enhances confidence in particle measurement data throughout the calibration year.