"David Combs" wrote in message

For safety from CO, we keep the window open a few inches,
always, allowing boiler-updraft to drag in fresh air.

Problem: leaves (southern Westchester county) and then
snow, potentially 100% covering the grate, dangerously.

What to put over the grate to keep leaves and snow
away from it.


Happens that six months ago I (surrepticiously) retrieved from our garbage
some old half-inch pieces of plywood.

Sounds like you are making a nice haven for rodents. Very thoughtful of you
as they like warm cozy places to live. .

I'd run a proper vent up the side of the building with a screened air intake
at least 48" above the ground. Not seeing your setup I can't give exact
methods, but you can replace a window pane and use PVC in periscope fashion,
or a through the wall vent that is commonly used for fresh air intakes.