Mechanical Elements

Things like Temperature, Humidity, Shock, and Vibration. Fire-proofing.

Vital for aerospace.

Humidity

• https://www.eevblog.com/forum/beginners/how-to-make-a-dc-fan-survive-1-year-in-99-humidity-at-25c/ - A discussion of fans in a high humidity environment. All 3 failed at 99% humidity (in 200 days), due to rust on the ball bearings. A good use of one of the humidity / temperature controlled chambers. This also suggests that removing humidity from environments will slow rust on mechanical parts (which is what I've heard of cars that are in the desert, i.e. that they don't rust much. This may also explain microchip being in Arizona. But rust must be desirable, as the desert is lifeless.).

DIY Humidity Chamber

It's trivial to build a humidity chamber. Get an aquarium pump and a fish tank. Use an arduino, a relay, and an DHT11 sensor (or multiple) to regulate how often the pump runs. Put the fans or mechanical element in the tank, and cover it up. You can alternatively introduce air from the outside with a separate fan and some pvc pipe. This can be used to test rust on metals. Make it more corrosive, by putting it outside and exposing it to sunlight, as well as temperature differentials. Or, you can do what bell labs did, and just leave stuff on the roof to get hit by the elements.

Fire-proof / Fire-resistant

• https://en.wikipedia.org/wiki/Mineral-insulated_copper-clad_cable from https://www.eevblog.com/forum/beginners/fire-proof-ptfe-120vac-exension-cable/msg5892346/#msg5892346 A discussion on fire resistant mains cables, as well as cables that don't generate noxious smoke.