Wearing a hoodie while inside gas hood?

[BlindsClosed]

Hey everyone. I have a question. Actually two. But first - would it be safe to wear my sweatshirt hoodie inside the nitro gas hood? It would give such a more calming effect and feel like a pillow instead of a crunchy plastic bag sound. Also, that idea lead me wondering... how tight does the neck portion need to be to 'seal' the gas in? I already have everything and have a lock tie thing, I just want to double check how tight the hood should be or not, especially in the context of wearing a hoodie under that. Thanks so much for any advice/info!