Reports like this of people dying from CO poisoning in idling cars due to "clogged tailpipes" are disturbingly frequent. But how can this happen if the car is outdoors?
First of all, how does a modern engine respond if tailpipes are blocked? If they are obstructed enough that exhaust can't escape the system why doesn't the engine stall?
Second, since the engine does in fact somehow continue to run, how does exhaust end up in the cabin? I'm guessing that there's an obvious weak point at which the backpressure escapes the exhaust system, and that point must be near the cabin air intake? (But if that's the case, would setting the cabin airflow to recirculate prevent the intake of exhaust?)