You are encouraged to attend the defence. The details of the defence and attendance information is included below:  

Date:  Wednesday, November 26, 2025

Time:  10:30 AM – 12:30 PM (PT)

Defence mode:  Remote 

Virtual Attendance: via Microsoft Teams 

Please contact the Office of Graduate Administration for information regarding remote attendance for online defences. 

To ensure the defence proceeds with no interruptions, please mute your audio and video on entry and do not inadvertently share your screen. The meeting will be locked to entry 5 minutes after it begins: please ensure you are on time.  

Thesis/Dissertation entitled:   VALIDATING THE USE OF A MULTI-FRACTION SAMPLER FOR RECOVERING INHALABLE AND RESPIRABLE DUST MASS, AND METALS IN WORKPLACE AIR

Abstract: 

This study validated the Disposable Respirable Sampler (DRS) as an integrated, multi-fraction sampler for simultaneous measurement of inhalable and respirable aerosol mass and associated metals, following ISO 7708 definitions. The DRS consists of a disposable body with polyurethane foam, a PVC chimney, and a 25 mm PVC filter. Gravimetric analysis of the filter represents the respirable fraction, while the foam and chimney combined represent the inhalable fraction. Validation included laboratory gravimetric and chemical testing, followed by field sampling at three welding shops in Prince George, BC.

Gravimetric tests in a controlled chamber (25 °C, 50% RH) confirmed mass stability of all components over 3–4 weeks. DRS limits of detection (LOD) and quantification (LOQ) were 22/72 µg (filter), 41/137 µg (foam), and 183/610 µg (capsule), within ISO 15767 criteria. Chemical method validation was conducted using certified stainless-steel welding fume (SSWF) reference material at multiple concentration levels (0.1, 0.5, 1, and 2 × TLV). Analytical recoveries Analytical recovery values for the chimney + foam component ranged from 91.5–107.3% for Cr, 93.5–102.9% for Fe, 87.7–98.9% for Mn, and 90.6–107.1% for Ni, with method repeatability (CV) between 1.5% and 6.6%, and intermediate reproducibility between 3.0% and 9.7%, all within acceptable thresholds. Recoveries for the filter fraction ranged from 91.7–103.6% for Cr, 92.2–103.1% for Fe, 90.6–97.3% for Mn, and 91.2–99.8% for Ni, with method repeatability values between 0.8% and 5.4% and reproducibility between 1.0% and 6.4%, confirming robust analytical precision.

Field sampling compared the DRS with reference samplers (DIS, IOM+foam, Higgins–Dewell cyclones). For inhalable dust, DRS performance varied: 114% of reference values at Cariboo (CCC = 0.827), 72.6% at GAP (CCC = 0.287), and 97.6% at Stinger (CCC = 0.964), with a pooled mean of 91.5%. Respirable dust results were more consistent, with DRS measuring 0.156, 0.68, and 0.374 mg/m³ versus cyclone values of 0.13, 0.594, and 0.334 mg/m³, reflecting a pooled 15.8% oversampling. Metals analysis showed no significant differences between samplers for either fraction, indicating that gravimetric discrepancies were not due to collection efficiency.

This multi-site validation confirms the DRS as a reliable, field-ready tool for dual-fraction aerosol sampling. It closely matched reference samplers, with only a slight negative bias for inhalable dust under humid conditions and a modest positive bias for respirable dust. Metals results further support the accuracy of the DRS, highlighting its practicality as a disposable, efficient option for workplace exposure assessment.

Defence Committee:  

Chair: Dr. Jalil Safaei Boroojeny, University of Northern British Columbia  

Supervisor: Dr. Hossein Kazemian, University of Northern British Columbia  

Committee Member: Dr. Peter Jackson, University of Northern British Columbia  

Committee Member: Dr. Kerry Reimer, University of Northern British Columbia  

External Examiner: Dr. Mark Teo, WorkSafeBC