The Wiltshire Community Air Network, run by Wiltshire Council have started releasing Air Pollution Monitors to interested parties such as schools, businesses and individuals.
You can find out more about the network here: https://www.wiltshire.gov.uk/article/13735/About-the-Wiltshire-Community-Air-Network
Although the network is only just starting up, there are some already in place in Salisbury. Below is a map of the data currently available: