Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
An anesthesia machine is the federally defined “gas machine for anesthesia”: a device that delivers a general inhalation anesthetic and maintains a patient’s ventilation. It is used by anesthesia teams and by the clinic staff and buyers who equip them. For the ventilator it can include, see what a ventilator is; for the clinical specialty, see what anesthesiology is.
What an anesthesia machine is
Under 21 CFR 868.5160(a), a gas machine for anesthesia is “a device used to administer to a patient, continuously or intermittently, a general inhalation anesthetic and to maintain a patient’s ventilation.” FDA classifies it as Class II (performance standards).
What an anesthesia machine includes
The same regulation states that the device “may include a gas flowmeter, vaporizer, ventilator, breathing circuit with bag, and emergency air supply.” The word “may” matters: the definition lists what a machine can contain, and two of those parts, the vaporizer and the breathing circuit, are also regulated as devices in their own right.
| Component | What the regulation says it does | FDA class | Regulation |
|---|---|---|---|
| Gas machine for anesthesia (whole device) | Administers a general inhalation anesthetic, continuously or intermittently, and maintains ventilation | Class II (performance standards) | 21 CFR 868.5160(a) |
| Anesthetic vaporizer | Vaporizes liquid anesthetic and delivers a controlled amount of the vapor to the patient | Class II (performance standards) | 21 CFR 868.5880 |
| Anesthesia breathing circuit | Administers medical gases to a patient during anesthesia; provides an inhalation and an exhalation route and may include a connector, adaptor and Y-piece | Class I (general controls); exempt from premarket notification, subject to the limitations in 868.9 | 21 CFR 868.5240 |
How it works and how it is built
The federal definition describes the machine by what it does: it administers a general inhalation anesthetic, continuously or intermittently, and maintains the patient’s ventilation (21 CFR 868.5160(a)). Its construction is described only as a list of parts the device “may include”: a gas flowmeter, vaporizer, ventilator, breathing circuit with bag, and emergency air supply. The vaporizer is separately defined as a device that vaporizes liquid anesthetic and delivers a controlled amount of the vapor to the patient (21 CFR 868.5880). The breathing circuit is separately defined as the device that provides an inhalation and an exhalation route for medical gases and may include a connector, adaptor and Y-piece (21 CFR 868.5240). The regulations do not prescribe a single layout, so a given machine may be built with some or all of these parts.
Anesthesia versus analgesia gas machines
The regulation defines two separate devices. A gas machine for anesthesia delivers a general inhalation anesthetic. A gas machine for analgesia, 868.5160(b), is a device used to administer an analgesic agent to a patient, with a nitrous oxide-oxygen mixture given as an example. Both are Class II (performance standards).
Types and variants
The regulations name the following distinct devices that relate to the machine. Each has its own classification.
| Type | What the regulation says | FDA class | Regulation |
|---|---|---|---|
| Gas machine for anesthesia | Administers a general inhalation anesthetic and maintains ventilation | Class II (performance standards) | 21 CFR 868.5160(a) |
| Gas machine for analgesia | Administers an analgesic agent, with a nitrous oxide-oxygen mixture given as an example | Class II (performance standards) | 21 CFR 868.5160(b) |
| Anesthetic vaporizer (separately regulated part) | Vaporizes liquid anesthetic and delivers a controlled amount of the vapor | Class II (performance standards) | 21 CFR 868.5880 |
| Anesthesia breathing circuit (separately regulated part) | Provides an inhalation and an exhalation route for medical gases during anesthesia | Class I (general controls); exempt from premarket notification, subject to 868.9 | 21 CFR 868.5240 |
How FDA classifies the parts
The table above shows the practical consequence: the machine and the vaporizer are Class II, while the breathing circuit is Class I and exempt from premarket notification (subject to 868.9). A Class II device is subject to performance standards; see FDA’s recognized consensus standards for how standards are recognized. The circuit is classified as its own device; see anesthesia circuits.
Who uses it
The regulation describes the device by function, not by user. Anesthesia teams use the machine to deliver inhalation anesthesia; clinic staff and buyers specify and equip it. It is a medical device; see what a medical device is for the wider device category.
Common mistakes
- Treating the machine, vaporizer and breathing circuit as one regulatory category. They are three separate classifications (II, II and I).
- Assuming every machine contains every listed component. The regulation says the device “may include” them.
- Confusing a gas machine for analgesia (an analgesic agent such as a nitrous oxide-oxygen mixture) with a gas machine for anesthesia; the regulation defines them as separate devices.
FAQ
What is an anesthesia machine?
It is a device that administers a general inhalation anesthetic to a patient, continuously or intermittently, and maintains the patient’s ventilation (21 CFR 868.5160(a)).
What parts can an anesthesia machine include?
A gas flowmeter, vaporizer, ventilator, breathing circuit with bag, and emergency air supply, according to 21 CFR 868.5160(a).
How does FDA classify an anesthesia machine?
Class II (performance standards). The vaporizer is also Class II; the breathing circuit is Class I (general controls) and exempt from premarket notification, subject to 868.9.
Sources
- 21 CFR 868.5160, Gas machine for anesthesia or analgesia: https://www.law.cornell.edu/cfr/text/21/868.5160 (Cornell LII mirror of the CFR; checked 2026-11-03)
- 21 CFR 868.5880, Anesthetic vaporizer: https://www.law.cornell.edu/cfr/text/21/868.5880 (checked 2026-11-03)
- 21 CFR 868.5240, Anesthesia breathing circuit: https://www.law.cornell.edu/cfr/text/21/868.5240 (checked 2026-11-03)
