SKC PMI Personal Modular Impactor

Overview

The SKC PMI Personal Modular Impactor is a single-stage, size-selective aerosol sampling device engineered for occupational and environmental monitoring of inhalable particulate matter. It operates on the principle of inertial impaction—where airborne particles suspended in a 3 L/min laminar airflow stream are accelerated through a precisely dimensioned nozzle and deposited onto a substrate based on their aerodynamic diameter. This physical separation mechanism enables selective collection of PM₂.₅ (aerodynamic diameter ≤2.5 µm), PM₁₀ (≤10 µm), or coarse-mode particles (2.5–10 µm), fully aligned with U.S. EPA regulatory definitions (40 CFR Part 53) and ISO 7708:1995 standards for particle size fractionation. Designed for personal (worker-worn) deployment, the PMI integrates seamlessly with constant-flow sampling pumps such as the SKC AirChek TOUCH, ensuring stable volumetric delivery critical for gravimetric and elemental analysis. Its compact form factor (5.1 cm × 2.6 cm), low mass (70.9 g), and modular architecture minimize wearer burden while maintaining metrological integrity across field deployments.

Key Features

• Patented single-stage impactor design (U.S. Patent No. 7,334,453) optimized for 3 L/min flow rate with sharp, reproducible cut-points at 2.5 µm or 10 µm—validated against EPA reference methods.
• Modular configuration: PMI-PM₂.₅, PMI-PM₁₀, and PMI-Coarse variants share identical mechanical interfaces; conversion between fractions requires only the PMI Coarse Ring (P/N 225-3512) and second filter cassette.
• Disposable, pre-oiled 25 mm porous plastic impactor substrate eliminates cleaning, re-oiling, and associated variability—reducing maintenance overhead and improving inter-sample consistency.
• Delrin® filter cassette with integrated stainless steel support mesh ensures flat, uniform filter seating and minimizes edge leakage during gravimetric weighing.
• Chemically inert materials: aluminum inlet (precision-machined), PVC exhaust housing, PTFE O-rings (inlet), BUNA-N O-rings (exhaust)—compatible with organic solvent extraction and acid digestion protocols.
• Tool-free media exchange: filter cassettes detach via quarter-turn release; replacement takes <15 seconds without disassembling the impactor stage.

Sample Compatibility & Compliance

The PMI supports a wide range of final filter media—including polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), quartz fiber, and mixed-cellulose ester—selected per analytical requirement (e.g., NIOSH Method 0500 for total dust, EPA Method IO-4.3 for metals, or ASTM D6216 for PM₂.₅ mass). Its performance meets U.S. EPA equivalency criteria for PM₂.₅ and PM₁₀ samplers under 40 CFR Part 53, Subpart C, and conforms to ISO 7708:1995 for aerodynamic particle size classification. The device is routinely deployed in GLP-compliant industrial hygiene surveys and satisfies chain-of-custody documentation requirements when paired with SKC’s calibrated AirChek TOUCH pump (NIST-traceable flow verification). All components are RoHS-compliant and free of intentionally added PFAS.

Software & Data Management

While the PMI itself is a passive, hardware-only sampling device, its operational data integrity is maintained through integration with SKC’s ecosystem of digital tools. When used with the AirChek TOUCH pump, real-time flow logging (±2% accuracy), temperature/pressure compensation, and event-tagged start/stop timestamps are stored internally and exportable via USB or Bluetooth to SKC’s AirData software. This enables automated calculation of sampled volume, adherence to OSHA 1910.1200 and ACGIH TLV® exposure duration thresholds, and audit-ready reporting compliant with 21 CFR Part 11 (electronic signatures, audit trails, data immutability). Field calibration is supported using the PMI Calibration Adapter (P/N 225-358) and primary-standard rotameters or electronic calibrators traceable to NIST.

Applications

• Occupational health monitoring: Quantification of respirable and inhalable dust fractions in mining, construction, pharmaceutical manufacturing, and foundry operations.
• Environmental compliance: Ambient PM₂.₅/PM₁₀ characterization near industrial fencelines, waste transfer stations, or biomass combustion facilities.
• Toxicology and exposure science: Collection of size-fractionated aerosols for in vitro cytotoxicity assays or speciation analysis (e.g., EC/OC, water-soluble ions, transition metals).
• Method validation studies: Reference sampler in inter-laboratory comparisons evaluating new sensor-based PM monitors per ISO 11097.
• Indoor air quality (IAQ) assessments: Personal exposure profiling in office buildings, schools, and healthcare settings where coarse-mode allergens (e.g., pollen, fungal spores) coexist with fine-mode combustion byproducts.

FAQ

What flow rate is required for proper operation?
The PMI must be operated at a nominal 3.0 L/min, maintained within ±5% tolerance throughout sampling—achievable using SKC AirChek TOUCH or equivalent constant-flow pumps with built-in flow control.
Can the same PMI unit collect both PM₂.₅ and PM₁₀ in one sample?
No—PMI is a single-stage device; PM₂.₅ and PM₁₀ require separate sampling events using dedicated PMI-PM₂.₅ or PMI-PM₁₀ configurations. For simultaneous coarse/fine measurement, use the PMI-Coarse variant with dual-cassette setup.
Is the impactor substrate reusable?
No—the 25 mm pre-oiled porous plastic disc is disposable and supplied in sterile, individually wrapped packs (25/pk or 50/pk); reuse compromises collection efficiency due to oil depletion and surface contamination.
Which filter media are recommended for gravimetric analysis?
For NIOSH/OSHA-compliant mass determination, 37 mm PVC filters (e.g., SKC P/N 225-1001) are standard; for high-temperature applications or low blank requirements, quartz or Teflon filters are preferred.
Does the PMI require annual recalibration?
The PMI has no active electronics or moving parts; however, its dimensional tolerances must remain verified. Users should perform annual visual inspection and flow-profile validation using the PMI Calibration Adapter and certified flowmeter per SKC Technical Bulletin TB-012.