Let’s start by diving into the differences between the two types of air quality measurement equipment you will encounter as you set up your own Clarity network: a traditional reference monitor, and a non-reference grade low-cost sensor such as the Clarity Node-S.

By the end of this lesson, you’ll be able to:

1. Understand the difference between reference monitors and Clarity devices.
2. Understand the benefits and challenges of both reference monitors and Clarity devices, and learn how both can be used to complement one another.

Reference Monitors

A reference station in Mexico City, Mexico.

Reference monitors are not available for all regions, but when in operation, they are most often managed and operated by a government entity as part of air quality management programs that provide consistent, long-term assessment of ambient pollutant levels. Companies may also be required to operate reference monitors to comply with regulations related to their industry.

To be used for regulation, reference monitors need to be operated and maintained according to specific procedures that comply with guidance set forth by a regulatory agency.

Reference monitors typically cost tens to hundreds of thousands of dollars to purchase, require specialized monitoring infrastructure (trailer, temperature controlled housing, etc.), and need to be operated and maintained by qualified technicians.

Due to cost and maintenance requirements, reference networks are often relatively sparse and do not provide air quality information for all areas of concern.

These monitors provide high-level of accuracy if properly operated and maintained.

Examples of regulatory agencies:

   ◦ United States Environmental Project Agency (US EPA): In the United States, data from these instruments are used by US EPA to assess attainment of the NAAQS (​​National Ambient Air Quality Standards)

   ◦ European Environment Agency (EEA) in the European Union.

Types of names for reference monitors you may encounter:

   ◦ Federal Equivalent Method (FEM), Federal Reference Method (FRM) in the U.S.

   ◦ Reference Station, Monitor or Site. 

   ◦ Regulatory or Regulatory-Grade Monitor or Site.

Clarity Node-S: A type of air sensor

These air sensors, like the Clarity Node-S, can supplement the existing networks of reference monitors by providing data at locations without any reference monitors.

With their lower cost, smaller footprint, and fewer technical requirements, the use cases expand beyond regulation to the following:

   ◦ Increase public awareness of air quality issues.

   ◦ Inform environmental and public policy recommendations.

   ◦ Support environmental justice work.

   ◦ Form part of hybrid networks, which employ both reference and low-cost monitors

   ◦ Monitor in economically developing areas and/or remote locations.

   ◦ Conduct air quality and public health research.

While easier to use, calibration is an important step of air sensors to ensure the data quality is able to meet the project goals.

Ten Clarity devices undergoing collocation for calibration in Quezon City, the Philippines.

Reference Monitors vs Air Sensors

Let’s take a side-by-side look at the differences between traditional reference monitors and low-cost sensor networks.