Parts of an Autoclave – Labeled Schematic and Functions

All 14 parts on the diagram

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The chamber 7

Chamber The load is sterilized here, in steam under pressure.
Door It closes the front of the chamber steam-tight.
Chamber pressure gauge It shows the pressure, or the vacuum, inside the chamber.
Thermometer It shows the temperature in the drain line, the coolest spot.
Steam trap It lets air and water out, then closes when steam reaches it.
Chamber drain Air and water leave the chamber through this opening.
Exhaust valve Opened after sterilizing, it lets the steam out of the chamber.

The steam line 7

Jacket The space between the two shells. Steam fills it first and keeps the chamber wall hot.
Safety valve It opens to let steam out if the pressure gets too high.
Steam supply valve It opens and shuts the steam line from the boiler.
Steam strainer It catches dirt carried in the incoming steam.
Pressure regulator It keeps the steam pressure steady in the sterilizer.
Jacket pressure gauge It shows the steam pressure in the jacket.
Operating valve It sends steam from the jacket into the chamber.

How this list was compiled: Every name checked on 2026-10-01 and kept only where at least two of these use it. (1) A 1943 United States Army medical supply school textbook, Text Book Volume III, Medical Equipment, General (public domain, National Library of Medicine copy), full text at https://archive.org/details/14220980RX3.nlm.nih.gov : body, jacket, chamber, door, chamber gauge, jacket gauge, thermometer in the air and condensate line, thermostatic trap, operating valves, safety valve, steam strainer, steam supply valve, steam regulator valve, chamber drain, exhaust valve, and what each does. (2) Plumbing: Manual of Instruction for the Plumbing Trade, 1982 (ERIC ED246304), part 31 and its sterilizer schematic, full text at https://archive.org/details/ERIC_ED246304 : strainer, steam-supply valve, pressure regulator, jacket, jacket pressure gauge, pop-off (safety) valve, chamber, steam-in-chamber valve (the operating valve), chamber pressure vacuum gauge, thermometer, chamber steam trap, exhaust valve, and what the operating valve, safety valve, trap, thermometer and strainer do. (3) Wikipedia, Autoclave, https://en.wikipedia.org/wiki/Autoclave : chamber, jacket, door, the drain that air is forced out through, the steam trap, what an autoclave is used for. Labels, hints, detail lines and position notes were written for this site. Licence: own work

The drawing: Own drawing from plain geometry; nothing traced. Licence: own work

How it works

The parts of an autoclave are drawn here on one cutaway schematic of a steam-jacketed model. Tap a ring to read the name of the part and what it does, then press Quiz me.

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The way the steam goes

Steam comes up the supply line through the steam strainer, the steam supply valve and the pressure regulator, and fills the jacket round the chamber. The operating valve then sends it from the jacket into the chamber, where the load sits.

The way the air goes out

Steam is less dense than air, so it fills the top of the chamber first and pushes the air down and out through the chamber drain. The thermometer sits in that drain line, and the steam trap closes once only steam reaches it.

Two dials look alike. The stem of the chamber pressure gauge reaches the inner shell; the jacket pressure gauge stops at the outer one.

Questions and answers

What are the main parts of an autoclave?

A chamber that holds the load, a door that closes it steam-tight, a jacket of steam round the chamber, pressure gauges, a safety valve, a thermometer, and a drain with a steam trap that lets the air and water out.

What does the jacket of an autoclave do?

The jacket is the space between the outer shell and the inner shell. Steam fills it before any is let into the chamber, so the chamber is surrounded by steam.

What does the steam trap do in an autoclave?

It stays open while air or water flows through it, and closes when steam heats it. That lets the air and the water out of the chamber and holds the steam in.

What is an autoclave used for?

It sterilizes things with steam under pressure. Autoclaves are most often used to sterilize medical instruments and supplies, and laboratories use them too.