[Speedslug]

The end of the duct where the ventilation mixes with the air out side ( the exhaust end) only needs to be 3.3 meters away from any air that might come back in to the room.
The experts tell us thet that is enough room for the exhaust gases to get diluted into the fresh air out side.

The blocking I had suggested between the bottom of the window and the sill with a hole in it to put the duct through would have let you run the ductwork to the bottom edge of the screen with out the need for having any ductwork hanging outside the window.
By blocking the bottom of the window you would prevent any exhaust from getting back in the room and the suction side (at the torch) would force your make up air to come the other rooms in you house and over your shoulders ensuring that you keep breathing uncontaminated air.
The blocking would also keep the bugs from coming in that window.
If you want to you could use Perspex or Plexiglas as blocking to let light in.

You may find that keeping the bugs out with a towel wont work for you.
There are just so many of the darn things out there and it seems that they have nothing to do all day long but look for a way to get in to your house.


I am at a loss of what to tell to about the "muffler" you mentioned.

Any thing that is going to reduce the amount of noise from your fan is also going to reduce the flow of air through it. I am sure that there are ways to use mufflers but I think they have to do with increasing the volume of air the fan can push to make up for the amount the muffler slows it down.

I would not use a muffler myself unless the fan was extremely noisy and then I would look at getting a different fan.

As for where to place the fan, I would put it at least a full meter from the end of the flame so there would be no chance of the fan getting any heat from the flame but inside the room.

I would put the reducer the reducer 25 cm from the end of the flame.
You can use what ever is handy to hold the reducer up. I have seen them screwed to coffee cans with the cans filled with dirt to give them some weight and placed at the back edge of the bench. I have also seen them hanging from two wires that get hooked to the middle of the window when it is open. these can be un hooked and taken down when you want close the window again.