Fwiw perhaps our efforts to develop a cheap air quality monitor might be of interest, see http://ourairquality.org/ This design uses a NodeMCU/esp8266 Wifi board and the esp-open-rtos framework. It supports the Plantower PMSx003 family of sensors, and the BME280 and a few other temperature and humidity sensors. A dc3231 real-time-clock is supported as an option. Some features that might differentiate it are:
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It records all the data from the PM sensor, more that one sample a second. This might help with quickly changing air quality, such as is common from close sources of pollution, and with mapping.
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It compresses the data and can store a few days of data on the NodeMCU flash, a circular buffer. This allows it to work offline for a few days, or with intermittent Internet access without losing data.
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The compressed data can be pushed to a server or pulled from the device.
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It is designed to minimise data manipulation in the data logger and stores the complete raw data from the PM sensor including the crc, and logs data as a journal. This is an attempt to make it more credible on cross examination.
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A wall mounted case is also described, folded from a single piece of fluted plastic. This is a attempt (perhaps misguided) to make a cheap case.
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The server side software is not as well developed and still under development.