M12 Vent Plug Airflow: 9 to 300 L/h on One Thread

An M12x1.5 vent plug from one supplier passes 16 litres of air an hour. From another supplier, 300. The thread is the same, the hex is the same, the nylon body looks the same. What differs is the membrane area behind the body and the pressure each supplier chose to test at, and neither of those appears anywhere on the part you are holding.

Buyers put those two figures side by side every week. That comparison is what this page breaks.

Seven suppliers, one thread, numbers from 9 to 300 L/h

Every figure below was read from the supplier's own product page on 28 October 2026, next to the pressure it was measured at. Where a supplier publishes no pressure, the cell says so. Nothing here is an average across a range unless the supplier published it as one.

Put the millilitre rows into litres per hour and the set runs from nine to three hundred. That is a factor of thirty three between two parts that both screw into the same M12 hole, sold at prices that differ by far less than thirty three times.

Airflow and water entry are bought with the same money

Three of those suppliers publish four grades of one M12 body and print both numbers for every grade. Read the pairs.

The trade holds in all three columns. Eight times the airflow costs eight times the water head. The plug that passes 300 litres an hour keeps water out at one metre. The plug that holds eight metres passes sixteen litres an hour. You cannot buy the top of one column without buying the bottom of the other, because both numbers come from the same membrane area and the same pore size.

All four Ortac grades carry the same IP68 label. So does the Bepto brass part rated above 5 bar, and so does the SR Lvents part at 100 kPa. The IP code is telling you that no water got through in the test the supplier ran, not how much pressure it would have taken. A buyer who shortlists on IP68 alone has sorted nothing. We wrote about that gap separately in what each IP rating actually tests.

One supplier sits off the curve. Bepto publishes 1200 ml/min at 70 mbar and more than 5 bar water entry from the same M12 brass body. Against Ortac's nearest grade that is roughly half the airflow and twenty five times the water pressure. Either that membrane is a genuinely different construction, or the two figures were taken under conditions the page does not state. Ask which one before you design a gasket around it.

Three ways a datasheet number stops being comparable

The pressure is missing. SAB lists 16 L/h and Lucid lists 50 L/h with no reference pressure at all. A volume per hour means nothing without the differential that pushed it. Ask for the millibar figure, or treat the number as decoration.

The unit is normalised to membrane area. Bepto's aluminium range quotes 1.2 L/min/cm2 at 70 mbar for every thread from M5 to M40. That is a property of the membrane, not of the part. It cannot be compared with anyone else's ml/min, and it does not tell you what an M12 body passes. The same product line also lists 800 ml/min at 70 mbar for its M12 aluminium version, and that is the figure you can use.

One number is quoted without its pair. Airflow alone cannot be judged, and neither can water entry alone. A vent that passes 300 litres an hour but gives up at 0.1 bar is the wrong part for a cabinet washed with a pressure hose, and a vent that holds 9 bar but passes 6 litres an hour is the wrong part for a 200 litre enclosure that swings 40 degrees.

What to put on the drawing before you ask for a quote

• State the differential you need to equalise, in mbar, not the airflow.
• Ask for airflow and water entry at the same reference pressure, and say which pressure.
• Ask whether the membrane is expanded PTFE or acrylic copolymer on a nylon support. The two behave differently in oil mist and in UV.
• Ask which grade of a multi-grade line is being quoted. The cheap line item is usually the low flow grade.
• Ask for the water entry test duration. Bepto states 60 seconds, PUW states 40 seconds, and a longer hold is a harder test.

Our vent plug size chart works out how much airflow a sealed enclosure actually needs from its internal volume and temperature swing, using ideal gas behaviour and no product data at all. Run that first to get your required figure, then compare it against what a supplier claims at the pressure you specified. If the claimed airflow was measured at a pressure you will never see, the comparison is not a comparison.

The same trap shows up in service. A blocked vent still passes its IP68 retest, so the label outlives the airflow, as covered in what the IP68 test leaves out.

Where the numbers on this page came from

Every figure was read from the manufacturer's or distributor's own published page on 28 October 2026. No value has been estimated, averaged across a range, or rounded beyond the millilitre to litre conversion, which divides by 1000 and multiplies by 60.

• GORE PolyVent Standard and High Airflow, screw-in series
• GORE PolyVent High Airflow M12x1.5
• Ortac plastic ventilation plugs, four M12 grades
• Fastpoint plastic ventilation plug M12
• SAB VPB-02 vent plug M12x1.5
• Lucid hygienic vent plugs
• Newelfin 010VV datasheet
• Bepto low profile hex protective vent, nickel brass
• Bepto waterproof protective vent, nylon
• PUW plastic vent plug PUWM12x1.5-6
• PUW stainless vent plug PSM12x1.5-6
• SR Lvents M12 vent plug SR568X

If you are holding a datasheet that does not fit any of the patterns above, send it over with the drawing. We will tell you which column is missing.