How to Evaluate lLow-Cost Sensors by Collocation with ...

How to Evaluate Low-Cost Sensors by Collocation with Federal Reference Method Monitors

National Exposure Research Laboratory Office of Research and Development

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Contributors

EPA - Office of Research and Development Teri Conner, conner.teri@ Andrea Clements, clements.andrea@ Ronald Williams, williams.ronald@ EPA - Office of Air Quality Planning and Standards Amanda Kaufman, kaufman.amanda@

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Introduction and Objective

Recent technological advances in air quality monitoring are providing smaller, lower-cost, sensor-based monitors.

? These low-cost sensors can measure some of the same air pollutants that more costly reference monitors can measure.

? But how good are they?

The goal of this presentation is to provide instructions for evaluating low-cost sensors by collocating them with reference monitors and comparing measurements of the two to determine the "trustworthiness" of low-cost sensors.

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Background: Reference Monitors

What are Reference Monitors? Why do we need them?

? The Clean Air Act requires every state to establish a network of air monitoring stations to monitor criteria air pollutants that must meet National Ambient Air Quality Standards (NAAQS). Not all criteria pollutants are measured at all stations.

? The measurement instruments and methods used at these regulatory monitoring stations are called Federal Reference Methods (FRM) or Federal Equivalent Methods (FEM).

? The FRM/FEM instruments must meet rigorous standards for accuracy and reliability (see 40 CFR part 53 for details). These instruments are "The Gold Standard".

? In this presentation, these FRM/FEM instruments will be referred to as reference monitors for simplicity.

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Background: Reference Monitors vs Low-Cost Sensors

Here is how low-cost sensors compare with reference monitors:

Typical Purchase Cost Range Operating Expense Siting Location Staff Training

Data Quality

Operating Lifetime Used for Regulatory Monitoring?

Reference Monitors

$15,000 to $50,000 Expensive

Fixed Location (building/trailer needed) Highly trained technical staff

Known and consistent quality in a variety of conditions

10+ Years (calibrated and operated to

maintain accuracy) Yes

Low-Cost Sensors

$100 to $2500

Inexpensive

Portable (basic weather shielding)

Little or No Training

Unknown and may vary from sensor to sensor and

in different weather conditions

Short (1 year) or Unknown (may become less sensitive over time)

No

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