My Husband Made Deep Fried Chicken Thighs, He Was Running

My husband made deep fried chicken thighs, he was running low on oil vegitable oil, so unbeknownst to me he used a small amount of some old used cooking oil (a clear layer of it at the top of the bottle) that was sitting on a shelf for over a month or so. Are we in danger of getting Botulism from eating the chicken?