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Humidity in the shop - how much is too much?

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  • Humidity in the shop - how much is too much?

    I got a new weather station/thermometer thingy for Christmas. I have the main display in my den, a remote sensor outside, and one in the shop. Been looking at the humidity reading the last couple days and was wondering how much is too much with regards to tools and equipment rusting etc.

    My shop is 1000 sq. ft metal pole building, with tall open ceilings, and is well insulated. The main heat is electric which I have set to keep it above freezing. Coldest I've seen in there was about 36 degrees, this with an ambient of 25 degrees at the time. I fire up the wood-stove when I know I'll be working out there for awhile (maybe once a week or so).

    Here is the data from today.
    Outside ambient temp = 56 degrees
    Inside temp = 53 degrees
    Humidity inside = 78%
    Humidity outside = 90%

    The sensor has ranges where it displays either "dry", nothing, or "wet". It currently says "wet". I'm thinking wet is not good. I will admit that since the shop was built in 1996 I've not noticed a particular problem with rust, but I was just a bit surprised to see the humidity so high in there. I'm in the pacific northwest btw.

    Is there a specific humidity level that is a danger zone as far as equipment preservation goes?


  • #2
    Your target should be between 50 and 60%. Thats what I maintain for my customers with your general specifications. Using a dehumidifyer and piping the condencate drain out of the space should remidy your problem.



    • #3
      living by the sea my shop is mostly above 80% all year round and nothing rusts long as you dont try to heat the place .
      then the problems start
      I've had peices of bare metal in there for years and ..theres no rust on them.
      as long as you keep both machines and shop at the same temperature you should have minimal of problem even at 90% humidity.
      thats as far as I can work out what happens in my place.
      all the best..mark


      • #4
        If nothing rusts, than you don't have a rusting problem.
        Location: North Central Texas


        • #5
          I've used dew point charts as a rough guide of where my shop is at. Here's a decent chart in degrees C and F:

          I'm not sure my analysis is 100% correct and am open to correction but for your outdoor temp and hum (55F, 90%), the dew point is roughly at 52F. This means that when you open the doors and let a blast come in ... poof !! you have condensation if your machinery or tools are BELOW 52F from the chart.

          Also, if you run a dehumidifier, you may need to raise the temp above 65-ish to prevent ice-up on the coils of it ... unless those newer than my old beast control that.



          • #6
            When I was using the corn oil and water as a coolant, the whole front of my mill rusted, table you had to stay after. Rodents in my cnc mill was why that stopped. I had sticky traps everywhere. I was afraid they'd chew the wiring up. and it has plenty.

            My shop sweats something terrible when it heats up.

            It is pretty cool in there lately, I have been wearing my carharts to machine in, with apron, with 2pair gloves (leather w/kevlar inside) on in the morning.
            Not real happy, I should have spent more shop money on insulation and less on beer. I'll take care of that next year.
            With all the fancy tools, tooling, the shop has not paid a nickel into the household in two months. Too busy upgrading I guess. (the harley is waiting too.)



            • #7
              David you need to build the northern canadian mousetrap. A five gallon bucket of water a round piece of wood on top with a small (MOUSE SIZED) rectangle cut out of it. This is hinged with a wire pivot near the middle. A piece of wood for the mice to walk up to the top paiece of wood,at the rectangular cutout that pivots. Stinky piece of cheese at the end. When the weight of the mouse passes over the fulcrum point suddenly mr mouse falls out of sight into the bottom of the bucket. Then the wooden door falls back to its previous position awaiting the next victium. (two gallons of water in bottom of bucket) Result one wet pissed off and soon drowned dead mouse bastard. Had a bad mouse problem at the cottage years ago. This kooky contraption accounted for no **** dozens of mice. I havent even seen a mouse there in years. We keep two of these traps around but I think we killed off there clan .Too bad I say. Good luck Dave


              • #8
                A Museum technician told me that 56 % humidity was the thresehold limit for metal.
                I marked my humidistat in the shop with a red line at that point, and when the needle hits it, the dehumidifier goes on ( the one job within my skill level !)
                I have no rust problems after 6 years with this setup
                Green Bay, WI


                • #9
                  I worry about the linear scales. They said non-condensing atmosphere. I got two of them in use.