Hide Website Header and Menu on specific page

Hi

I’d like to hide the website header and and menu on a specific page. I have found two CSS codes below but neither seem to work:

1st CODE

.page-id-2476 #header, .page-id-2476 #footer {
display: none;
}

2nd CODE

#page-id-2476 #header, #page-id-2476 #footer {
display: none;
}

Any idea why the code is not working and what the correct code would be?

many thanks

Flavio