Can anyone point to where it says if doors do or do not block line of sight?

"A figure has line of sight if the player
can trace a line from at least one corner dot in his space to a
corner dot in the target space without crossing a brown wall or
the top of a door.

If all lines of sight are traced through walls and/or doors, then
the target is not considered to be within range (regardless of
the number of spaces away)." (p. 21)

In short, doors block LOS.

Yes, inside a house doors block the line of fire as there are no dots to trace a line.

flames said:

Actually, there are dots on some of the indoor tiles, all Hallways (numbered and Corner Hallway) have dots on them. Corner Hallway even has a door in between the two Corner Hallways just to block the dots and LOS.