Sorry Kevin,
Your way off base here, Steam locomotives have always and will always throw sparks, it's thier nature.
We keep a thirty foot cleared zone( NO burnables) on either side of the track centerline and have still had problems with fires.
in twenty years operating and maintaining steam locomotives, I've seen oil burners start fires, (especially ties and the cab floor) wood burners start fires(ties, trees, roofwalks, the Conductors dog !) Coal burners start fires (ALL the above!(Except the Dog!!)) No amount of screen can stop all the sparks and still allow the fire to draft( we've been trying for thirty years !).
We keep our locomotives in top shape, have "NO FIRE" zones where you can't open the firebox door, spray water on the ROW, motorized fire patrol behind the train and have a network of fire trails thru all the worst areas and still frequently are restricted from operating thru the forest, especially during periods where the winds exceed fifteen MPH.
In the CYA era in which we operate, sometimes a diesel is the only option the "powers that be" may accept.
For what it's worth.......Jerry