A dairy barn mid winter in Saskatchewan, when the ventilation system isn't working. There are about 400 animals in here - see if you can count them. There are also several people, but I'm not sure who.

Hope you're not a smoker..........

I think I see you in there.

twh,
Over here, our dairy sheds only have 3 exterior walls, the front of the shed (where the cows enter and leave the rotary platform) is open, this negates the need for any sort of ventilation system.
I'd be interested to see what the inside of this barn looks like when it's not running, just to compare the difference between your stuff and ours.
At any one time during milking here, you'd normally only have 50-80 cows on the platform, 400 of them sounds like a real nightmare, especially if there was a power failure.

I occasionally repair the chairs for a large dairy farm. Let me explain. The farm dairy has 3 mechanics, a computer technician, the farmer, his sons and wife. Lunch is a big deal in France and runs about noon till 2pm. When I get invited we languish over 4 courses, 'sample' the Bordeaux, calvados or cider, talk, smoke, argue politics, machinery etc. Oft times the milk-test lady who seeks for TB or brucellosis bugs, the vet'nery, or the feed-rep get their shoes under the table too. The old farm chairs get a right pasting, often rocked on the back legs or stomped with boots, hence the regular application of Titebond, elbow grease, replacement parts and injections of Chair Doctor, for Rule #1 in France is: Never, Ever Throw Anything Away! My first visit was a revelation - for the cows milk themselves! Or rather the Robot does, under the direction of the computer. Each cow has a collar with a unique transponder. She can enter the milker any time she likes, but only gets a ration of nuts 3 times a day, when the robot slips in under easy and washes, blow dries & milks her. 3 milkings a day adds another liter of milk to the bottom line - which pays for the whole shebang in 3 years to the tune of $350,000 +. The shed is open at both ends, the sides are slatted for venting and the cows may wander off into the pasture as they like or eat in from the racks, coming back in as their udders yearn for milking. Young cows train with a small ration before they lactate. The [ahem] merde is collected by a sweep arm and goes back on the land as fertiliser. Whole maize silage is the main feed in the winter, grown on the farm, grass in summer as this is some of the most productive dairy land in France.
The advantage is compound, for the farmer contracts his labor, tractors, mowers, tedders, balers etc. out to others while his milk-cheques are on auto-pilot. A second robot just got commissioned. Can't say I've ever seen a fog like that in the shed. In the house, oui!

Our winters are 5 to 6 months long and the temperature approaches -40 for a day or two in at least one month, so the barn is totally enclosed and has curtains that can be opened for ventilation. This barn has six 24 foot ceiling fans to circulate the air. Without the fans in the winter, the fog sets in.

The cows are separated into 4 pens and go to the milking parlor one pen at a time. I don't know what happens when the power is off.

This is the only dairy barn that I've been in and I understand it isn't very nice compared to some others.

Life is hard by any standards. The farmer, his wife and sons have difficulty keeping hired help. The milking is 4 AM and 4PM. Dinner is never on time and there are no days off. They plant and harvest their own crops and tend to the animals between milkings and until after dark. I didn't know that cows need their nails done!

When I go back, I'll take more pictures.