Dehumidifiers in your work shop

[briman87]

Do you have water constantly draining to the sump or only when it rains?  

John

Only when it rains and it usually has to be a hard rain or a lot of rain

[jteneyck]

Only when it rains and it usually has to be a hard rain or a lot of rain

Then sealing the floor and caulking that expansion strip may get you back to where you were prior to installing the drains in terms of RH.  

John

[AHill]

It's an urban legend that static buildup can cause an explosion.  Wood dust isn't wheat flour.    

John

Not an urban legend - at least not in commercial systems.  And it doesn't need to be dust to ignite.  Sugar factories have had explosions and fires.  Sugar grains are much larger than salt.

https://dustsafetyscience.com/dust-colle...nsylvania/
https://www.nederman.com/en-gb/knowledge...n-industry
https://www.finewoodworking.com/forum/sawdust-explosion
https://www.lumberjocks.com/topics/25054
https://s3.amazonaws.com/jpw-assets/4/0/...man_en.pdf  (Powermatic's PM-1300 Dust Collector Owner's Manual recommends ductwork grounding.)

PVC is a pretty reliable source of static electricity.  There's less static in a high humidity environment, so the risk is lower. 

I've never personally known anyone struck by lightning either, but that doesn't mean it doesn't happen.

For my peace of mind, I'd rather ground my ductwork even if the probability of static electricity induced explosion or fire is remote.