Bethesda, MD – News4 – Two women in Bethesda, Md. are recovering after their home filled with carbon monoxide late Tuesday morning.

According to Montgomery County Fire spokesman Pete Piringer, the pair are lucky that it happened during the day because they were alert enough to realize something was wrong and get out.

Piringer said if this had happened at night, the women might not have awakened.

Piringer said the home in the 9400 block of Rockville Pike is overrun with carbon monoxide. Investigators believe it came from the furnace, which the women turned on this morning for the first time this fall.

Authorities said it’s crucial for people to get furnaces checked now for any problems before it turns really cold.