Air Filter Ratings Explained: MERV, G-Class & F-Class

Why Ratings Matter

Every air filter is rated for how effectively it captures particles of a given size. Choosing the right rating is a balance: too low and you let particles through; too high and you restrict airflow, forcing your system to work harder. Understanding the classification systems helps you get that balance right.

The G-Class and F-Class System (EN779)

Most of the filters we manufacture use the European EN779 classification, which is widely used across Australia.

Coarse / Pre-Filters (G-Class)

• •G3 — Captures larger particles such as dust, lint and hair. Often washable and used in return air grilles.
• •G4 — Finer than G3, capturing smaller dust particles and pollen. The go-to all-rounder for most residential and light commercial HVAC systems.

Fine Filters (F-Class)

• •F5 — Medium efficiency, capturing finer airborne particles that G-class filters miss.
• •F6 (60–65%) — Improved fine-particle capture for commercial environments.
• •F7 (80–85%) — A common choice for offices, schools and healthcare pre-filtration.
• •F8 (90–95%) and F9 (95%+) — High efficiency for critical air-quality applications.

HEPA Filters

HEPA (High Efficiency Particulate Air) filters sit above the F-class range:

• •95% efficiency — Used in demanding commercial and industrial settings.
• •99.99% efficiency (H13/H14) — Medical-grade, for operating theatres, pharmaceutical and sterile processing.

What About MERV?

MERV (Minimum Efficiency Reporting Value) is the American rating system, running from MERV 1 to MERV 16. You will sometimes see it on imported equipment. As a rough guide:

• •MERV 6–8 ≈ G4
• •MERV 9–12 ≈ F5–F7
• •MERV 13–16 ≈ F7–F9

Choosing the Right Rating

1. General dust control → G4

2. Better air quality / allergies → F5–F7

3. Critical or healthcare environments → F8–F9 or HEPA

4. Odour and gas control → add a carbon filter stage

Remember: your system has to be able to handle the pressure drop of a higher-rated filter. If you are unsure, we can advise on the right balance for your specific equipment.

Need Advice?

Our team has manufactured and specified filters for every kind of application across Brisbane. Request a quote or call us on 07 3800 3448 and we will match the right rating to your system.