Educational Resources

Basic Inhalation System Components

Metered-Dose Inhaler
A metered-dose inhaler is comprised of four main parts:

• Canister
• Metering Valve
• Spray Orifice
• Plastic Mouthpiece

Pressing down on the inhaler releases a measured dose of medicine, which is then inhaled into the lungs.

Metering Valve
In pressurized metered-dose inhalers, the metering valve must accurately deliver a measured amount of product and should be reproducible for each dose delivered. Metered-dose inhaler valves function by filling the metering chamber with product, sealing off this chamber from the remaining formulation in the canister when the valve stem is partially depressed, and then releasing the contents of the chamber through the valve stem upon further depression (actuation). The valves should retain their prime charge over fairly long periods of time. However, it is possible for material in the chamber to return slowly to the main body of product. The degree to which this can occur varies with the construction of the valve and the length of time between uses (actuations). Puff-to-puff dosage variability due to inadequate valve priming may lead to therapeutic failure.

3M offers a variety of valves to help ensure suitability for your formulation and patient use regimes.

View or download our Inhalation Glossary