The system we have developed is called Thingy:AQ The original system was developing specifically to meet the requirements for the USA EPA and other US governments bodies for their Wildland Fire Challenge. If you are interested you can find the background information here: https://www.brushelectronics.com/blog/
We have subsequently re-architected the system for the more general use cases. There are two main solutions were are supporting. The original remote node concept has been retained plus we have added satellite up-link capability per node. This was required as the coverage in remote regions where Wildland fires are a significant problem do not have LoRaWAN or even LTE coverage. This new model is currently being tested in the field. The other solution we addressed was the decoupling of our gas sensor subsystem from the rest of the node to enable the subsystem to be integrated with third party environmental monitoring and logging systems. The initial deployment of these is scheduled to happen in April.
Back to your specific question, I used the SDS011 PM sensor in our initial system. The node powers up the PM sensor every 5 minutes, flush the air through the sensor for 30 seconds, then take a number of samples, average the results, and powers down the PM sensor. As well as reducing the power consumption, this also significantly extends the life of the sensor. The SDS011 is rated for 8000 hours (less than a year) of continuous operation. Using the sampling approach described here, the life is effectively extended to 5 years. However, to be clear, without the right environmental protection for these sensors, they will cease to operate reliably within months. The system, as originally developed, had a three stage filter on input and exhaust to reduce the impact of the environment (weather and bugs) shortening the life of the sensor and system in general. It costs significantly more to protect the sensor than the cost of the sensor itself.
You cannot just switch off the power to the sensor (well you can but it won’t help) you also need to isolate the RS232 bus to prevent the sensor being power-up buy the RS232 transmit pin from the processor.