AQMesh - Low Cost Outdoor Air Quality Monitor
AQMesh is the only commercially available and proven low-cost system for monitoring air quality. The product combines a robust hardware platform with the latest sensor technology and GPRS communication, cloud-based data processing and online access. AQMesh pods are manufactured in the UK to the very high standard demanded by users in the other environmental sectors already served. Experience in development of monitoring instruments has allowed electronic noise to be reduced in such a way that the best possible sensitivity is achieved from the sensors used. Gases are measured using the latest generation of electrochemical sensors, which allow compensation for environmental factors and sensitivity to 5ppb. Particles are measured using a light scattering optical particle counter.
AQMesh v4.0 pods are characterised at manufacture, to give the best possible performance, as shown below:
AOMesh offers an effective means of gathering air quality data from any location using a concept which is different to conventional monitoring equipment:
- Hardware (AQMesh pod)
- Cloud server
The small AQMesh pod is battery-powered. Power usage by the pod is minimised to ensure that the battery life is as long as possible. Raw signal strength from sensors is transmitted by GPRS to a cloud server. Readings cannot be downloaded directly from the pod itself.
The raw output from sensors is processed on the secure cloud server, including the mathematical processing which deals with cross-gas effects and environmental factors. AQMesh pods cannot function without the cloud-based system.
A secure web login gives access to data from the pod(s) and a dashboard for management of settings. See Data access for more information.
AOMesh can be used for a wide range of applications. As this type of product is so new, practitioners are only starting to appreciate the ways in which better data – high time resolution and high spatial resolution – can open up new applications. This list is just the beginning for low-cost air quality monitoring.
- Checking pollutant levels in a traffic tunnel and a ventilation shaft to confirm effectiveness
- Confirming that pollution along bus routes is improved by upgrading of exhaust processing on the local bus fleet
- Attributing local pollution around an airport to aviation and traffic sources
- Street canyon effects – measuring pollution across a road to understand the contribution made by local (traffic) sources and wider background pollution. More…
- Source apportionment of pollution – establishing where pollution of a particular profile is coming from
- Establishing where and when an industrial plume has touched the ground
- Fence line monitoring around an industrial site. More…
- Mobile monitoring (on foot) around an urban route to understand personal exposure
- Monitoring pollution at different levels up an urban high rise building to understand exposure with windows open
AOMesh is very simple to install: one of our users installed 20 pods in London in a morning. There are some simple steps and the video shows how easy it is to get up and running:
- Unpack, screw on antenna and remove pod from mounting (single security screw)
- Select location and secure mounting
- Connect battery and start initialisation sequence (10 minutes)
- Mount pod in position (single security screw)
- Log onto the AQMesh server to enter location coordinates and check data is transmitting
- Wait for data to stabilise (automatic flag)
Readings can be from as short an interval as 1 minute. The default setting is hourly readings, as this maximises the battery life and is suitable for most applications.
Transmission intervals can also be set by the user – the default is hourly.
Changing pod settings
User access is by secure login. Permission levels can be set by user to allow access to be restricted if required.
Online access allows the following to be viewed or changed:
- GPRS connectivity and data transmission frequency
- Reading frequency
- Sensor serial number (this must be changed if a sensor is replaced in order to pick up individual sensor characteristics)
- Time zone
- ppb to µg/m3
- View graphs and compare pods
- Download data
Online user access to the pod is available on two levels:
1 Default settings
As simple as possible for any user
2 Advanced settings are accessible by all users
- Allows improvement in accuracy through scaling
- When co-location with a reference station is possible
- Scaling using regression analysis
AQMesh pods can be powered in various ways. This allows flexibility of location, dependent on application or project type. The table gives an indication of how long a pod will remain powered using the different power options available.
AQMesh is a flexible platform which can accommodate various sensors.
AQMesh parameters available now
The product currently measures nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) using a new generation of electrochemical sensors. The standard product also measures pod temperature, atmospheric pressure and relative humidity.
Carbon monoxide (CO) and sulphur dioxide (SO2) can also be chosen as optional electrochemical sensors. AQMesh also offers measurement of total particle count, PM2.5 and PM10 using a light-scattering optical particle counter.
Future parameters and applications
The AQMesh platform can support a range of different sensors and additional parameters will be available in the future.
AQMesh data is accessed online and is available in two ways:
- Graphs presented online
- Data download
Data can be viewed or downloaded for any given time period and for any combination of parameters. Readings are generally accessible about 15 minutes after the data transmission time set. AQMesh.net also allows the facility for two pods to be compared online.
Data files include:
- Time – time zone can be set online
- Readings – ppb or µg/m3 for gases, P/cm3 for particle count
- Data flags – this indicates data which should be used with care or discarded, such as readings which are below the detection limit of the equipment or are during the stabilisation phase of a new, replaced or moved electrochemical sensor
- Scaling – changes to offset or slope applied by the user are shown in the data file
There are some differences between data files produced in the two different user modes – Default and Advanced:
How good are measurements?
AQMesh has been in development, global trials and available for sale since 2013. During that time, AQMesh v.3.0 showed that trends could be identified and the product was suitable for a number of air quality applications. Developments at the end of 2014 – improvements in electrochemical sensors and the AQMesh processing algorithms – have given a dramatic improvement in performance with AQMesh v.4.0 and v.4.1. The process and benefits of sensor characterisation at manufacture include optimal correction for environmental factors, correction of gas span and baseline offset.
The most popular method for measuring AQMesh performance is by co-locating AQMesh pods immediately next to an air quality monitoring reference station and carrying out regression analysis of AQMesh readings against those from the RTMS, where a higher R2 shows a closer match in readings from the two types of equipment (an R2 value of 1.0 is a perfect relationship, and is unlikely to be achieved even by two co-located reference instruments; R2 of 0.0 would indicate no relationship at all between the instruments).
R2 of >0.6 for NO2 is generally considered to be a strong enough performance for AQMesh to be suitable for most air quality monitoring applications.
A number of independent comparison studies have been published online – please note any date / AQMesh version against the table above to establish whether the study relates to the latest version.
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