Siblings watching ours baby

SKs are 10 and 12. Ours baby is 1. I look after the baby the majority of the time and when it's a weekend with the SKs I very rarely leave DH to watch baby. But I do need to go to a different room to cook dinner or something for example so I ask DH to watch the baby and he says no problem.

But so many times he then asks one of the SKs to watch the baby while he does something and he leaves the room. We don't really have any safe spaces anymore as baby can climb over everything and try to jump off. If DH is still in the room, or just leaves the room to grab something then I don't have a problem with that. But I'm not comfortable with the baby not having constant adult supervision. I don't think it's okay to go have a 20 minute shower or be outside. I've told him I'm not comfortable with this.

He says he has no choice as I've told him I'm busy and if he needs to do something then he needs to do it. If I need to do something I do it with the baby or not at all,I don't put the SKs in charge.

The SKs love playing with baby but they're not very responsible as they're easily distracted and don't know what babies can and can't do safely. Though I am not comfortable with any non adult watching my baby.

Am I being unreasonable here? In my mind a 1 year old needs constant adult supervision as something can happen in the space of a few mins. I'd love to hear how others feel about this.