Data accuracy and efficiency are of paramount importance during ambient air monitoring. Low-cost sensors are affected by various factors like temperature, humidity, windspeed, dust, etc. The paper explains the effect of each factor on the sensor performance. Direct exposure to these may cause sensor failure, erroneous data generation, and frequent calibration. Based on these limitations the active sampling and passive sampling method in sensor-based systems are compared and reasoned to determine which principle ensures better data quality and efficiency.

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PASSIVE VS ACTIVE SAMPLING FOR SENSOR-BASED
AMBIENT AIR QUALITY MONITORING

2. AMBIENT AIR MONITORING DEVICES:
OR
REFERENCE STATION LOW-COST SENSOR-
BASED
Low-Cost
Affordable
Compact Device
Easy to fit
Sensitive to External Environment.
(Temperature, Humidity, Wind Speed, Dust)
Data Accuracy decreases with time.
INTRODUCTION
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality Monitoring

3. - Effect of Temperature and
Humidity on sensor depends on
the extremity of the conditions
and time duration of exposure.
- Both positive and negative
effects are observed with
increase in temperature.
- Particulate Matter sensors are
highly sensitive to Relative
Humidity.
- Temperature and Relative
Humidity are negatively
correlated.
TEMPERATURE:
Photoionization Detector (PID)
Electrochemical Sensors
Nondispersive Infrared (NDIR) (no effect)
RELATIVE HUMIDITY:
PM2.5 : Underestimated
PM10 : Overestimated
RH > 70-80% Mass Concentration
Particle Number
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringFACTORS AFFECTING SENSORS

4. DUST
- High dust concentration PM10 (>300-400 μg/m3 )
causes dust deposition on the sensors.
- RH > 85% : PM agglomerates and gets stuck on the
sensors.
- Construction and Mining sites.
- Dust laden roads.
- Drilling sites.
Erroneous Results Frequent
Maintenance &
Replacement
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringFACTORS AFFECTING SENSORS

5. - Transport and Dispersion of Air pollutants is affected. (PM2.5, PM10).
- Diffusion rates and kinetics of redox reactions are affected that generates
erroneous results.
WIND SPEED
Turbulence, Wind gusts, High Wind Speed affects sensor
performance.
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringFACTORS AFFECTING SENSORS

6. High Volume Air Sampler
(First Generation)
Continuous Ambient Air Quality Monitoring
Stations - CAAQMS
(Second Generation)
Low-Cost Sensors
(Third Generation)
Active Sampling Devices Passive Sampling Devices
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringCLASSIFICATION

7. Exposed
Sensors
- Sensor are directly exposed to the Environment.
- Sensor gets highly affected by:
Used in conventional sensor-based systems.
- Reduced Data Accuracy
- Frequent Maintenance and Replacement.
- Reduced Working Life.
TEMPERATURE RELATIVE
HUMIDITY
HEAVY
DUST
HIGH
SPEED
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringPASSIVE DEVICES

8. Sensors are placed in an enclosed unit.
- The system draws in a specific volume of air
using a pump at a particular time interval.
- Not affected by Ambient Conditions.
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringACTIVE DEVICES

9. Parameter Passive Sampling Active Sampling
Sensor exposure to ambient
conditions
Yes No
Air sampling using a predefined
airflow
No Yes
Influence of temperature, humidity,
dust or wind on data
Yes No
Maintenance
Frequent due to reduced
working life of sensors
Minimal with quarterly
cleaning activity
On-site reference gas calibration No Yes
Collocation against reference-grade
systems with R2 >0.85
No Yes
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringCOMPARISON

10. E – BREATHING
TECHNOLOGY
(Active Sampling Based)
BIOMIMICRY OF THE
HUMAN LUNGS.
INHALES
(325ml air sample)
EXHALES
(325ml air sample)
ANALYZING USING DIFFERENT
SENSORS
Collocated against
Reference Stations
R2 > 0.85 – 0.9
No effect of External
Environmental Factors
Better Data Quality
(High Accuracy and Precision)
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringOIZOM’S OFFERING

11. Oizom has a wide range of sensor-based air quality monitoring systems for all kinds of applications which
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calibrated against the standard reference system.
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringOIZOM’S OFFERING
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Passive Vs Active Sampling For Sensor-based Ambient Air Quality MonitoringOIZOM’S OFFERING