I know this doesn’t help you directly, but that’s of the things I love about my shop automation. I use the GRIT Automation system and it’s got a specific trigger for air cleaners. The trigger has a built in particulate sensor that is customizable. When it gets tripped, the filter comes on until the particulate level falls below a preset level, then it turns off. 

It’s probably not worth the money to build your own trigger with a sensor, but there are other home automation system like SmartThings or HomeKit that you might be able to use. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".