This is something to keep in mind the next time (or hopefully before) you have problems with a high efficiency gas appliance.
Our area was impacted by Winter Storm Vulcan last night, which left us with lots of drifts due to the high winds.
A co-worker came in this morning and told us that his on-demand water heater didn't work this morning and that they smelled gas in the basement. He got everyone out of the house and called the gas company. They came over, checked for leaks (said that they were required to) and then trudged through the snow to the back of the house to check the vent.
The snow had drifted up high enough to block the vent. The water heater would come on, try to blow the exhaust out and then shut down. Once the vent was cleared, everything worked fine.
About a half hour later, another co-worker came in and told us that her furnace stopped working just before she went to bed. Her husband checked a few things in the basement and then went outside to check the vent. Again, the snow had drifted up high enough to block the vent. Once he cleared the snow, they had heat again.
We should all remember that during a significant snow event we should keep an eye on the exhaust vents for our furnaces, water heaters, dryers, etc. If you are going on vacation, instructions should be left with someone to have them check the vents if you think they are low enough to be impacted by drifting snow.