Only once it has reached full pressure. Steam escapes noisily through the lid locking mechanism for about a minute first (escaping steam is used to engage the mechanism, which makes it fail-safe because without the mechanism engaged it will never reach full pressure).
>It has two pressure settings
Only on the more expensive model. Cheaper version only has the higher pressure mode. But I have the cheaper version and I have never wanted a low pressure mode. It seems redundant because it already has slow cooking mode.