How long does sterile stuff stay sterile?

My dentist, for example, sterlizes instruments before using them on me, but they are spread out on a tray in a room with no special air filters AFAIK.

How long can those instruments be considered sterile while sitting out like that?

Same question about when I open a package of gauze that says it’s sterile (“guaranteed if unopened”).

Same question applies to surgical instruments. Is there anything special about the treatment of the air in an operating room that preserves a sterile environment? Or is it controlled just by making sure every object in the room is strerile coming in?

They’re ‘sterile’ in the sense that they’re not contaminated with any infectious agents from another patient; this isn’t exaclty the same as saying that they are free from all microorganisms, which are all around us anyway, even in the air we breathe.

Depends on the OR you are talking about. Many operating rooms are designed with laminar flow ventilation that is designed to make the table an ideal environment.

Even with perfect laminar flow and air sterilisers an instrument in a waiting room will remain sterile for less than a second onc exposed to the air. You are in the room, the dentist is in the room, the dust from a dozen earlier patients is in the room. All those things are shedding microbes at an astounding rate.

Nope, it’s not close to sterile, it’s hopefully just not infectious.