Help! carbon monoxide detector went off!?

i am not in the house. i am babysitting 2 young kids. the 5 yr old is next door, me and the 2 year old are outside (laptop). i am 15 and scared shitless. my dad is on his way. we got out of there the minute the alarm went off, but all the windows were open and mutliple fans were on! i want even using any appliances. it went of first about 20 minutes ago but only for a second, so we went outside for 10 minutes or so and we were fine but now that is has gone off again and this time for real, i am scared. no one has gotten the symptoms (headache tired dizzy vomiting ect.) but the kids are okay right!?!