Best practices
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Best Practices
Environment
- Keep the device away from direct sunlight, radiators, and fireplaces — it is sensitive to temperature and lighting changes.
- Position the inlet away from localized emission sources unless intentionally measuring them.
- For indoor use, avoid placement near HVAC vents or drafts.
Sampling Configuration
- Sample frequency:
- Ambient immission monitoring: 180–600 seconds (3–10 min)
- Direct emissions from wood stoves (µg vs ng range): 10–30 seconds
- Note: increasing frequency may increase noise.
- Airflow:
- Minimum 40 mL/min, maximum 400 mL/min (hardware-dependent).
- Higher airflow improves signal strength but loads the filter faster.
| Pollution Level | Daily Avg BC | Recommended Airflow |
|---|---|---|
| Heavy pollution | >2000 ng/m³ | 50 mL/min |
| Typical urban | ~500 ng/m³ | 100–250 mL/min |
| Low pollution | <500 ng/m³ | 300–400 mL/min |
When Auto Flow Control is enabled, the device adjusts airflow automatically based on measured BC concentration — reducing flow when BC is high (to extend filter life) and increasing flow when BC is low (for better signal).
Signal Quality
Signal-to-noise ratio improves with:
- Higher BC loads
- Higher air volume per sample
- Smaller sample spot diameter
Filtering: Apply median/average filtering (denoise slider) to reduce noise. The rolling average is closer to the "real" value than individual data points.
Calibration: Always calibrate after every filter change for reliable filter status indication and accurate measurement.
Filter Management
- At the default airflow in a typical urban environment (~500 ng/m³), a filter lasts approximately 3–5 days.
- In heavily polluted areas, a filter may saturate in 6–12 hours.
- The filter is considered saturated at approximately 30% attenuation. Beyond this, accuracy degrades — values are flagged in the CSV.
- The Airflow Reference table in Settings helps estimate filter lifetime for your conditions.
Supported Filter Papers
| Filter Paper | Scattering Correction Factor |
|---|---|
| Pall T60A20 | 1.0 |
| AE33 Filter | 0.75 |
| AE51 Filter | 1.0 |
Other filter papers can be supported by determining their scattering factor. Send a sample to jd@bcmeter.org for calibration.