Whomever purchases these needs to look at the background in those pics.
I wish you well in selling your gear OP and I was interested until I looked at the price and saw the pics.
You cannot keep miners in such conditions and expect them to last long.
Further, you certainly should not keep them in such conditions and then sell them for over top dollar.
Specifically, the lack of filters and high RPM fans on the S4 pull every bit of crap laying around and lay it in patterns across the hash boards. When you have humid periods the moisture mixes with the patterns of filth and becomes further pushed in nooks and corners of components.
Depending on the the exact makeup of the crap you have laying around versus what someone else may have is how fast the break downs start to occur.
Pull one of the S4s at random, pull the covers, and take a magnifying glass to begin viewing the side of the components which would be against the incoming flow of fans and you will begin to see what I mean.
If miners are kept in a dirty, filterless environment then expect to have early death.
Having said that you can clean them up and get filters on them sooner than later.
Unfortunately you cannot stop anything organic, such as rust, but you can stop other, milder organic growth, and remove the lager pieces of buildup.
YMMV, Buyer Beware, and on and on, but I have seen a buddy of mine make the same mistake.
#1 clean the area and keep it clean.
#2 Filter, filter, filter and you still have issues in any home environment, but not as bad as without.
I would be interested if it weren't for price and quality.
These should be priced much lower.
Good Luck and I hope you are clear to people regarding what they are getting.
How long have you had them and how many times have you pulled the covers?
I am not going to ask if they were kept in a positive or negative pressure environment...
I just saw this, and I'm really not sure what to make of it. The conditions the miners are in, in the pictures, are not at all as you describe them. They are not humid environments, nor are they dirty.
In front of the breaker, the humidity is always about 37%-40%, as there is a big dehumidifier about 6ft away. As far as dirt goes, I don't really even know where you think it would come from. There are 3 with asthma in the house, so if the air had dirt floating around in it, it would be well known and taken care of immediately.
In the bay, the area where the miners are was swept before they were put there. Looking closely I do see a few leaves came in, but I doubt any got to the miners as they seem too far away for that. As for humidity, the humidity in this area was about 48% all last week. There is a 25ton, 7-axis custom CMM about 30ft in front of where the miners are. It cost about 1 million dollars to make, and it is sensitive to temperature, humidity, dust, etc. The whole room is controlled and monitored for everything, though I will admit that may have been slightly compromised while the door was cracked.
On top of all of this, the miners were only run in these places from 7pm Monday to 9pm Wednesday and Noon Tuesday to 5pm Thursday, to ensure they did not experience any damage during transport, and a final check for no Xs or -s in the ASIC reporting. I don't think they could have experienced any damage in less than 3 days. Previously all of the miners were in a server closet type room, which was air conditioned and had an exhaust duct that went out the roof. If you pay attention to the fan grills, you will notice they are all shiny and have no rust. The miners all down now, and will be until they are purchased.