Humidity levels, what is acceptable

[UncleJoe]

I live in Eastern North Carolina and it is pretty humid in the summer. I have some tools that are rusting and I decided to tackle my shop humidity issues. The shop is a 600sq garage not attached to the house. I insulated it and it has 2 garage doors. I have a large window a/c unit which makes the shop usable during our 90-100 degree July-August time period. The a/c unit also has a dehumidifier mode.

I also have one of those digital inside/outside thermometers and it shows humidity inside the shop.

Yesterday, the humidity inside the shop was 88% so I turned on the dehumidifier and a few hours later it as 72% and the shop was noticeably more comfortable.

So what is the realistic target humidity level I should have to prevent rust and such problems? As I type this at 8 am the humidity outside according to the weather site on the internet is 96%.

 

[Falcon67]

Prevent rust? We get single digit levels here and things still rust. People start complaining at about 45% RH. 50% and under would be a good target, but your climate may not allow that.

http://www.rockler.com/articles/workshop-humidity.cfm

 

[mayday0017]

Inside your house with your HVAC running if it is setup correctly you are in the ballpark of 50ish % (+/- 10)

Well here in Houston anyways...

 

[LutzTD]

when I worked in the shop there were some guys that just had the touch. whatever they touched rusted, this was in a humidity controlled environment. I mean machine tables, fixtures even gage blocks, would have rusty finger prints. We usually were able to combat it with a coat of light machine oil.

 

[1967marti]

i was in Lowes the other day and i saw that kobalt is selling these little sponge-things that you toss in your tool box and it is suppost to stop rust.... In the navy we would install a sticky-backed version of the same thing inside out radar gear to keep the rust away. I think Kobalt is even adding some chemical to their plastic tool-boxes to keep the rust away....

 

[bd8134]

The humidity on my ac is set at 50%, it sometimes goes lower 45%. I have a dehumidifier that comes on at 60%. I see no noticable surface rust on tools or materials.

 

[wb2vsj]

when I worked in the shop there were some guys that just had the touch. whatever they touched rusted, this was in a humidity controlled environment. I mean machine tables, fixtures even gage blocks, would have rusty finger prints. We usually were able to combat it with a coat of light machine oil.

We had a guy at the machine shop that was the exact same way. Everything he touched oxidized.

For the OP, that's NC fer ya! I finally installed a big-*** window AC unit in my garage. Should have done it sooner. (I'm near Raleigh)

As for the proper humidity levels, I can only speak to a data center environment, about 50%. Lower than that and we start to get ESD (Static electricity) issues.

 

[EOC_Jason]

I think what some of the people are talking about is Zerust. I use them in my gun safe. I *think* they have a liner you can use in your tool boxes. Whatever product you choose though it has to be in an enclosed space, you can't use them out in the open as it will just dissipate.

Anything to lower the RH & temperature is good, but keeping a light coating of oil is probably your best prevention.

 

[djjsr]

My experience -

If you want an air conditioned shop, you have to keep the doors closed all the time.

My shop has been around 76 degrees and less than 50% humidity for many summers. If I have the doors opened for a while when moving something, the outside air comes in and the moisture will condense on anything cold, which is just about everything.

This year my AC unit quit. The temperature in the shop is now higher, usually in the 80's and the humidity is up around 60 to 70%. I can leave the doors open all day without getting any wet floors or tools.

I run a couple of fans. I don't think I'm going to fix the AC.

 

[geotek]

Just got a danby for my basment from HD. In two days it pulled the humidity down from 88% to 65%. I've got it set to 30% but i've bottomed out in the low 50's. Temp is in the High 70's. I figure for a basement in an hold house that is probably the best i'll get. For a garage it'll be a mix of how much do you want it running $/hr and humidity drop. Every time you open the door you'll be back at the start. I say coat everyting in oil, none of the namby-pamby penetrating oil, use some manly stuff, axle grease or thicker!

 

[Busted_Knuckles]

Ive had the A/C on in the shop for months now, for rust and mildew prevention purposes exclusively. Ive not spent but a couple hours out there this year. I am also in the habit of wiping my tools down with WD40 prior to putting them away.

I do transmission and axle work, Ive got hundreds of black oxide tools, and its a full time job keeping them from rusting.

I think ZERO humidity is what to shoot for, and you'll land where you land, but the lower the better. If you're experiencing static shocks, you may have arrived.

 

[buzz4041]

50% humidity is a good level and achievable. I keep a dehumidifier running in my shop and set it to 50% and it has been a big help on the rust factor over the last 4 years. I can honestly see a big difference since I put it in.

 

[Angelfire]

Anything above about 20% is miserable to me! We're usually in the single digits so rust is highly unusual. We actually add humidity to cool our houses etc

 

[E.T.Privott]

the tool box liner may have a little something to do with it, how much oil or grease may be something to look at. the sweat on your hands, not wiping them down w/ oily rag...... your going to hand its not just one thing but a few things that can help beat this problem. i grew up in NC. and now live in the panhandle of FLA. so i can speak from both sides about the ongoing fight you are up against. this bucnh of wrench jockys well know if anybody knows how to fight and win this problem !!!

 

[fstbusa]

you guys are all talking relative humidity which has to do with what temperature you are at. The relative humidity is well...... relative to the temperature at which you are measuring.

If you want to compare humidity levels, you either need to include at what temperature you want your humidity % at or talk absolute humidity and have a reading like lb moist air per lb dry air or the # of grains per lb dry air.

IMO 50% RH is a good target to shoot for. That is typically what most of our homes are in the summer with the a/c running.

 

[racer7x]

Nothing to do with humidity levels but I have been using Fluid Film in the spray can the last few years for rust prevention in my shop and it works pretty well. Does not evaporate and hangs on for a long time.

 

[MadMechMaster]

Fstbusa is onto it. Without getting int the Psychrometric chart, you basically want the steel items in your garage to be over the dewpoint temperature for the current conditions. Any colder, and there will be condensation.

AC is good, but as soon as an overhead door is open you get can condensation if the steel is cold enough. I cover my table saw, mill and lathe to keep air off in my unheated garage.

Basically, 50% at 60° will be good to 50°. A heater can help to lower RH.

 

[MadMechMaster]

For me there are only a few weeks, when the seasons are changing, that it is difficult to prevent condensation.

 

[abstamaria]

I live in a high-humidity, tropical environment, and my cars belong to an era when Zinc plating of body panels wasn't in vogue. Consequently, I have had to pay some attention to this subject. From what I've read, at over 60% RH, rust will begin to form. At below 45%, wood will begin to dry up and shrink - not a problem for most, but some of you may have vintage cars with wooden frames or trim or guitars for the garage band. The manufacturer of our piano recommends 55%, and I think that most musical instrument makers recommend about that range. That is the range I aim for.

When I turn on the AC, humidity plummets to 35 to 40%. When I'm not in the garage or workshop, I rely on a portable dehumidifier, on the perhaps mistaken theory it uses less energy. i've been doing that for ten years. The good thing is that a rust film doesn't form on brake rotors, which used to happen in my old garage. So I second the motion on 50% or so.

I hope this is useful.

Andy

 

[EOC_Jason]

It's currently 82F & ~70% RH outside here in North Houston and it feels WONDERFUL! We are getting some nice dry wind from the North because the Hurricane is over in LA. Usually the RH is closer to 100% and it SSSSSUUUUCKKKKSSSSS....