TL;DR — The US EPA’s Enhanced Air Sensor Guidebook provides specific information on recommended practices for siting and installing low-cost sensors. By choosing an appropriate location for both individual sensors and the placement of a sensor network, and following best practices for air quality sensor installation, you can establish an effective air quality monitoring network that meets the project’s goals. 

The US EPA Enhanced Air Sensor Guidebook

This blog is part of a series that highlights key themes from the US EPA Enhanced Air Sensor Guidebook, an updated version published in 2022. The guidebook covers a variety of topics involving low-cost air quality sensor use.

Today we’ll be discussing how to site and install low-cost air sensor equipment for air quality monitoring networks. 

Properly siting and installing low-cost sensors is an essential part of establishing a successful air quality monitoring network and combines a variety of practical and technical considerations in alignment with the overall goal of the project.

Identifying appropriate siting locations for low-cost air sensors

There are a variety of important considerations to make when determining the siting locations for low-cost sensors.

These considerations include choosing a location that:

  • Provides a representative sampling of the area’s conditions to collect the most useful data
  • Provides power and, if needed, internet access to run the sensor — although Clarity’s Node-S air quality sensor requires neither! 
  • Does not risk tampering or other security issues
  • Can be easily accessed for sensor maintenance
  • Experiences minimal interference from surroundings
  • Represents a relevant location for the overall goals of the monitoring network (i.e., if a sensor is meant to measure students’ air pollution exposure at a school, place the sensor in an area that will capture students’ exposure)

It’s important to start this process early on, as it can be time-consuming to find appropriate locations, as well as to secure permission to access the air quality measurement site.

It is often useful to identify more sites than needed when initially thinking of siting locations, as some locations will be eliminated due to not meeting practical requirements, such as security concerns or lacking access to power.

It is helpful to use the project’s purpose to guide siting. For example, if you want to understand the pollution exposure that particular communities face, such as children or elderly individuals, place devices that represent these populations’ exposure levels — such as daycare centers, schools, or nursing homes.

If you want to deploy air sensors in a country or area without an existing regulatory-grade monitoring network, you can deploy the monitors in a manner similar to the guidelines governing reference monitoring networks.

Driving siting selection based on the intended purpose of your monitoring network is a crucial aspect of ensuring the most relevant, effective locations are chosen for air sensor deployment. (Image source: US EPA)

The importance of collecting community input on where to site air quality sensors

When it comes to community air quality monitoring, it is essential that residents are surveyed on their air quality concerns and ideas they may have on desired monitoring sites and project goals. 

The figure above showcases the community input process employed by Brightline Defense, a non-profit organization based in San Francisco. By identifying priority populations, marking areas of concern, and compiling information about community input, the most effective air quality monitoring network can be implemented to meet the needs of the neighborhood. 
Valley Vision, an organization centered in Sacramento, characterizes demographic information and pollution exposure according to ZIP code in order to make informed decisions about sensor placement. Linking this information to health outcomes like rates of heart disease and asthma helps make meaningful connections between air quality and key outcomes.

Installing low-cost air pollution sensors

The US EPA recommends certain logistical considerations when it comes to installing an air sensor, which we’ll break down below.

General locations

In selecting the general location of your air sensors, it is essential to choose a site that suits the purpose of the air quality monitoring project.

For example, a project interested in the exposure of community members waiting at a bus stop near a busy road will place air quality monitors in different locations than ones meant to capture the ambient air quality in the city as a whole.

Access to the air quality monitors

Because air quality monitors have to be maintained after their initial installation, it is vital that they are installed in a location where they can later be accessed following deployment.

Ensuring access may involve determining permissions, requirements needed for access, and any other limitations that may affect how frequently, or when, you can access the location.

Power and communications

Different low-cost air quality sensors vary in their requirements for power, solar energy, and WiFi, among other factors, so it is crucial to pick an installation site that provides what is necessary for the sensors.

Choosing equipment with low maintenance requirements — such as the Clarity Node-S, which is solar-powered — can save significantly on operation and maintenance costs for the network as a whole. 

You must also consider requirements for electrical safety and waterproofing of the equipment. 

Other considerations include ensuring there is a sufficient network in place to support data communication from the sensor, whether this is through a cellular or WiFi connection.

Security

It is important to place air monitors in areas that are secure and protected from tampering and theft.

This can be done by placing the monitor in a more inconspicuous location, such as behind a fence or in an area with little traffic, out of arm's reach, and/or by having a small sign describing the project.

Placement

Because sensors are generally used to measure people’s air quality exposure, it is important to place them in the typical height range of the breathing zone — approximately 3-6 feet high.

If a project is trying to capture the ambient air quality in an area, the monitors should be placed away from pollutant sources that would potentially create local spikes (such as a fire pit) as well as away from pollution sinks like trees.

Photos

It can be helpful to take photos of sensor deployment to help with both documentation and data interpretation.

Try to use photos that capture nearby buildings, landscapes, roads (if outdoors) or windows, doors, and exhaust vents (if indoors) to understand and document what’s around the sensor. The best photos will also capture the area’s typical use.

The Clarity Dashboard has a feature allowing users to store an image of where they have placed each sensor in the network in order to maintain these records.

Additional documentation

It is crucial to create detailed documentation of the siting and installation process of the air quality monitors.

Create a deployment log to compile notes about sensor placement and maintenance. It is common to give each sensor a unique identifier to maintain organized records.

Other considerations

It is also important to consider the factor of time when selecting air monitor locations. 

If you wish to determine the differences in air quality before and after certain actions intended to decrease air pollution — such as an anti-idling campaign — it’s important to measure air quality both before and after the action was taken.

Once locations have been selected, survey the site to identify exactly where devices will be mounted, and ensure that you have the necessary tools and accessories to do so.

Siting and installation for a network of air sensors

An air sensor network can be defined as at least two air sensors that have been deployed at different locations to collect air quality data for a certain neighborhood or area.

When selecting the different locations for the air sensors in the network, you can consider:

  • The variations you expect to see in air quality levels across the area
  • What one site may capture over another, and what points of data are important to combine into the network’s coverage
  • How might the wind flow at play impact pollutant concentrations in different areas
  • It is important to place air sensors both upwind and downwind in any areas of concern, whether due to pollutant sources, hotspots, etc. to make comparisons between the locations
  • What meteorological data is important to include when interpreting data
  • Whether it is possible to use existing networks’ data to support the network
  • How many air sensors can the project afford to deploy as part of the network

Identify these locations on a map, ensuring the sensors are spread out from one another to achieve better spatial coverage.

The image above provides an example of how air sensor networks can be placed on different scales — whether for regional/urban networks, neighborhood networks, or at the microscale for networks placed in small areas. (Image source: US EPA)

It is invaluable to receive input from local air quality agencies, environmental consultants, university experts, and others who can provide key information and expertise on designing air sensor networks.

Establishing an effective network starts with siting and installation

Properly siting and installing air quality monitoring equipment is a vital part of establishing an effective monitoring network.

It is important to take stock of the many factors that come into play when determining the most ideal sites for sensors to be placed.

To learn more about planning, deploying, and managing a low-cost air quality sensor network, read our “Guide to Leveraging Low-Cost Sensors for Air Quality Monitoring 2.0” here.