Dov,

When you say “dry ammo”, what kind of ammo are you talking about?  Is there a risk of explosion from any kind of dust or fumes?  You also say the area is dry and hot which I would guess you are in the Southwest and for ammo storage, probably in the desert.

The self propelled fans would’nt do much in the way of ventilation and your concern about explosion proof motors is why I ask about dust or fumes being present.  If there are, roof mounted fans drawing from a system of ducts inside the building would be the answer and there is also the question of filtering this exhaust rather than just exhausting to atmosphere.  However, air supply fans and ducts would be required to provide make up air for the air being exhausted otherwise the exhaust system would be quite ineffective in the sense that without make up air, you would be trying to turn the building into a vacuum except for air that could whistle through door and window jambs and the like.

The other thing to consider is the temperature inside the building on the hottest days. Depending on the construction, the temperature in there could get really high and I don’t think it is good to store any kind of ammo at elevated temperatures. Yes I would say is the answer to your question about ventilation being necessary at all.  Again, if there are no fumes or dust, the easiest way would be to install motor driven, thermostat controlled wall fans for a simple cross flow ventilation.  Have them exhaust on one wall and draw in on the opposite wall (make up air) and at least this would keep the building in the approx. temperature range of the outside ambient. And oh! Don’t forget the bird screens.

Hope this helps a bit.

I did some work in a fireworks factory many many years ago and was given a spec to follow. All I can remember was that the temp and humidity level were important. I assume that dry air causes a greater risk of sparks.

We also used a supply air AHU to ventilate the space and keep down any build up of volatiles that might be spilt, dropped, given off etc.

Flame proof motors were also the order of the day.

Any I think we had to arrange the ductwork in such a way to avoid gas/fumes from getting out. Sorry my memory isn't brilliant as I was a young lad at the time..but I'm sure there must be some regs that you can peruse.

We also had backup systems in case of failure.

Friar Tuck of Sherwood

You might consider heat recovery exhaust fans that heat exchange between the outgoing and incoming air. If the outside air temperature is significantly lower or higher than inside your bunker this will save you a lot of money on the air conditioning and heating bill.

You probable also have dehumidifiers and humidifiers to keep the relative humidity within a specified range as well. Am I right about that?