The double down is an incredibly useful skill for dogs to have. It requires the dog to be in a down already, and then you tell them to place their head on the floor. It essentially tells them “I know that there is a lot going on around you, but I need you to remain calm and ignore it all”.
This skill takes practice, and in a situation like this where he is very close to the vacuum (which he doesn’t like), it takes a lot of trust, too. He needs to believe that I will keep him safe from anything that makes him uncomfortable, which means making sure that the vacuum never touches him.
Like any skill, we teach this in a low-distraction environment, and slowly work up to something more challenging like this. With practice, your dog can perform a double down anywhere regardless of what is going on around them.