Oh, that really sucks!!!
Very creative way to have a ventilation hose for a fan/blower!
The blowers we used, both 110v & 12vdc also were explosion safe. They nailed the company for them knowing they were a tool we needed.
Now you can buy blowers like the ones we used for less than a hundred bucks. Hoses also, which we were nailed by the sellers. I have no idea if they are any way near what we used as far as cfm and safety aspects. The ones we used were required to meet the specks.
There was one manhole in particular I'll always remember, it was located near a freeway on the overpass. It was there prior to the overpass being built so what they did was raise the neck to match the new road. Since the hoses were only 12 - 15 feet long and would never be able to cause a complete air change within the amount of time specified, the solution was to install an eight inch diameter PVC pipe. They also installed tubing we could attach our gas testers to. I'd guess it was 30 feet to the floor. When you start down the ladder, you start to wonder how much deeper it could be. Ha!
We had large vaults down in the big city in the middle of large apartment complexes that are equipped with air exchangers, alarms wired into the network operating center and included smoke, gas, high water, intrusion and others. They were a much nicer environment to work in, no generator noise and nothing to set up, just unlock, lift up the hand rail and open the door.
Don
🤠
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