ASTM D737 Air Permeability Test for Fabrics

ASTM D737-18(2023) Air Permeability Test: Which Fabrics Need Breathability?

Air permeability is an important sourcing parameter for sportswear, summer clothing, workwear, softshell fabrics, tents, filters and many technical textile products. Yet a higher air permeability result does not automatically mean better fabric performance. Some products need easy airflow, some need a controlled balance, and others depend on low permeability to block wind or contain air.

ASTM D737-18(2023), the current active version of ASTM D737, provides a standardized method for measuring the air permeability of textile fabrics. For buyers, the test is most useful when the test conditions, finished fabric construction and intended end use are clearly defined.

What Does ASTM D737 Measure?

ASTM D737 measures the rate at which air passes perpendicularly through a known area of textile under a specified pressure difference. It applies to many types of fabrics, including woven, knitted, nonwoven, layered, pile, coated, resin-treated and otherwise finished materials.

The test is widely used for commercial acceptance testing and product development. It can help buyers compare finished constructions, monitor production consistency and determine whether a fabric is suitable for an application in which airflow matters.

Which Fabrics Usually Need Higher Air Permeability?

Sportswear and Activewear Fabrics

Running tops, training garments, cycling panels and other high-activity products often need airflow to help release heat. Knitted mesh, lightweight polyester constructions and ventilation panels may therefore be designed for relatively high air permeability. The correct target still depends on garment position, climate, fabric weight, stretch and required coverage.

Summer Apparel and Lightweight Linings

Shirts, dresses, lightweight uniform fabrics and garment linings may use air permeability as one indicator of wearing comfort. Open construction can support airflow, but buyers should also evaluate opacity, strength, shrinkage, pilling and colorfastness. A very open fabric may feel airy while failing other product requirements.

Mesh, Netting and Ventilation Components

Bag pockets, shoe uppers, hat panels, mosquito netting and ventilation zones are often expected to allow air movement. For these products, airflow may be a primary function. Hole size, yarn strength, snagging resistance and dimensional stability remain important alongside the ASTM D737 result.

Selected Workwear Applications

Workwear used in hot environments may require better ventilation, especially in lower-risk areas of a garment. However, airflow should never be increased by weakening protection required for abrasion, chemicals, flame, weather or workplace hazards. Protective requirements must be defined before setting an air permeability target.

Which Fabrics Need Controlled Rather Than Maximum Airflow?

Softshell and Stretch Woven Fabrics

Softshell fabrics usually balance mobility, wind resistance, thermal regulation and weather protection. Excessive airflow can reduce wind protection, while extremely low airflow may make the garment feel less comfortable during activity. Buyers should specify the intended season, activity level and layering system instead of requesting the highest possible result.

Tent and Outdoor Equipment Fabrics

Different tent components perform different jobs. Inner tent mesh needs ventilation, while a rainfly or coated floor is expected to resist weather penetration. Air permeability requirements should therefore be assigned by component, not applied to the entire tent as one number. Tear strength, hydrostatic resistance, coating adhesion and UV performance may be more important for exposed outer layers.

Coated and Laminated Fabrics

PU coatings, TPU membranes, films and laminations can reduce airflow significantly. This may be intentional for wind or water protection. The finished material must be tested because coating chemistry, coating weight, film continuity, lamination quality and finishing conditions can change the result. The air permeability of an uncoated base fabric does not predict the value of the final coated product.

Filters and Technical Textiles

Filtration products need controlled airflow rather than unrestricted airflow. A filter that passes more air may also capture particles differently, so air permeability must be evaluated together with filtration efficiency, pressure drop, loading behavior and the applicable product specification. ASTM D737 alone is not a complete filter-performance evaluation.

Which Fabrics Generally Do Not Need High Air Permeability?

Windproof Shell Fabrics

A wind-blocking shell depends on limiting air penetration. In this application, lower air permeability can be desirable, provided the garment still meets its comfort strategy through design, mechanical ventilation or a suitable moisture-vapor pathway.

Inflatable and Air-Retention Products

Air bags, inflatable structures and other air-retention components require carefully controlled leakage. Their performance and safety may involve additional product-specific standards, dynamic testing, coatings, seam construction and finished-component validation. A low steady-state ASTM D737 result should not be treated as complete proof of final-product performance.

Barrier Covers and Protective Layers

Some industrial covers, contamination-control layers and weather barriers are intended to limit air exchange. For these materials, higher permeability may work against the design objective. Buyers should prioritize the required barrier function and specify relevant waterproof, chemical, particle, seam or aging tests as applicable.

Rainproof Outer Layers

A rainproof fabric does not necessarily need measurable air passage through its structure. Comfort may instead depend on water-vapor transfer through a membrane, ventilation openings or garment design. This is why air permeability and moisture-vapor performance must be specified separately.

Application Guide for Textile Buyers

Accuracy note: The priorities above are general selection guidance, not universal acceptance limits. The required value and test conditions must be agreed according to the finished product, relevant standard, buyer specification and target market.

Why Two Similar Fabrics Can Produce Different Results

Fiber content alone does not determine air permeability. A polyester fabric can be highly breathable, tightly wind-resistant or nearly air-impermeable depending on how it is built and finished. Important variables include:

• Yarn denier, twist, shape and filament count
• Warp and weft density or knit structure
• Fabric weight and thickness
• Weave, mesh opening and surface texture
• Mechanical stretch or spandex content
• Calendering, brushing and other finishing processes
• PU coating, film, membrane or adhesive lamination
• Test direction when the two fabric faces differ

For sourcing decisions, compare tested finished fabrics produced to the intended bulk construction. Do not assume that nylon is always more or less air permeable than polyester, or that a lower-GSM fabric will always pass more air.

What Buyers Should Include in an ASTM D737 Inquiry

A request that says only “breathable fabric required” is difficult to evaluate. A more useful inquiry should include:

1. End use: running jacket, workwear, tent component, bag panel, filter or another application.
2. Finished construction: woven, knitted, mesh, brushed, coated, laminated or layered.
3. Test standard and version: for example, ASTM D737-18(2023).
4. Test conditions: state the required pressure differential, test area, airflow direction, units and conditioning or sampling requirements according to the applicable specification.
5. Acceptance requirement: define a target range or maximum/minimum value based on product development and buyer needs.
6. Tested state: initial fabric, after washing, after weathering or after another relevant treatment.
7. Related performance: wind resistance, water resistance, moisture-vapor transfer, tear strength, tensile strength, abrasion or stretch recovery.

Frequently Asked Questions

Is a higher ASTM D737 result always better?

No. Higher airflow may support ventilation in activewear or mesh, but it can reduce wind protection or air retention in other products. The correct result is the one that matches the intended function.

Does ASTM D737 measure fabric breathability?

It measures air permeability and can support discussion of breathability when airflow is relevant. In everyday marketing, “breathability” may also refer to water-vapor transfer and wearer comfort, which require separate evaluation.

Can ASTM D737 be used for coated fabric?

The ASTM scope includes coated and otherwise treated fabrics. Buyers should test the finished coated construction and define the relevant face, direction and conditions. Separate waterproof, coating and moisture-vapor tests may also be required.

Does waterproof fabric have to be air permeable?

No. A waterproof construction may allow little or no direct airflow while managing comfort through water-vapor transfer, garment vents or product design. Waterproofness, air permeability and moisture-vapor performance are different properties.

Can results from ASTM D737 and another air permeability method be compared directly?

Not without reviewing the complete conditions and reporting units. Buyers should avoid direct comparison unless the methods, pressure difference, test area, specimen preparation and calculation basis are aligned.

Choose Air Permeability by Function, Not by a Generic Number

ASTM D737 data is valuable when it helps confirm that a finished fabric performs as intended. The best target is not automatically the highest or lowest result. It should reflect the product’s airflow, protection, comfort, durability and regulatory requirements.

For apparel, outdoor equipment and technical textile sourcing, define the end use first. Then agree on the finished construction, test version, conditions, acceptance range and supporting performance tests before comparing suppliers.

Technical reference: ASTM International, ASTM D737-18(2023), Standard Test Method for Air Permeability of Textile Fabrics. This buyer guide summarizes application considerations and does not reproduce or replace the official test procedure.