AATCC 30, ASTM E2149: Guide to Antifungal and Antimicrobial Testing for Textiles

In the textile industry, ensuring a fabric is “mold-proof” and “antibacterial” involves two completely different technical requirements. Simply put, AATCC 30 is an antifungal test designed to check if a fabric will grow fuzzy mold in damp conditions or rot (lose strength) due to microbial attack. On the other hand, ASTM E2149 is an antimicrobial test specifically for fabrics where the active agent is “fixed” to the fibers and does not leach out. It measures how effectively the fabric kills bacteria (like those found in sweat) upon direct contact. These two standards are the quality benchmarks for functional textiles used in outdoor, medical, and sportswear sectors.

AATCC 30: Background and Technical Definition

AATCC 30 is the authoritative standard for evaluating the antifungal activity of textile materials, formally titled “Antifungal Activity, Assessment on Textile Materials: Mildew and Rot Resistance of Textile Materials.” The technical core of this standard is to simulate environments where fabrics are exposed to long-term high humidity or soil contact to determine their resistance to mold growth and microbial degradation of the fiber structure. It assesses not only the aesthetic damage (mold spots) but also the structural integrity (tensile strength) of the fabric. It is the primary reference for determining the biological safety of outdoor tents, awnings, and textiles intended for maritime export.

Comparison of the Four Core Procedures of AATCC 30 (I-IV)

The AATCC 30 standard is divided into four independent procedures based on different usage scenarios. Each procedure utilizes different fungal strains and environmental conditions to evaluate fabric durability from various perspectives. Below is a detailed comparison of the four procedures:

Procedure No.	Test Name	Core Evaluation Goal	Representative Strains	Typical Products
Test I	Soil Burial	Evaluates rot resistance and strength retention after being buried in soil.	Natural soil microbial community	Geotextiles, sandbags, military canvas.
Test II	Agar Plate (C. globosum)	Evaluates the degradation resistance of natural fibers like cotton and linen.	Chaetomium globosum	Pure cotton fabrics, linen products.
Test III	Agar Plate (A. niger)	Evaluates surface mold growth and inhibitory zones.	Aspergillus niger	Standard apparel, outdoor furniture fabrics.
Test IV	Humidity Jar	Simulates mold resistance in confined, damp, and unventilated environments.	Mixed spore suspension	Export goods, indoor upholstery.

AATCC 30 Test III: Test Method and Operational Workflow

Test III is the most common antifungal procedure in commercial applications, primarily testing resistance against Aspergillus niger. The method involves placing the fabric on a non-nutritive agar plate inoculated with high concentrations of fungal spores. If mold grows on the fabric surface, it indicates the fungus is using the fabric as a food source; if no growth occurs, the fabric has undergone effective antifungal treatment. The operational workflow is as follows:

• Prepare circular test specimens approximately 3.8 cm in diameter, along with untreated control samples.
• Place the specimens on the surface of a non-nutritive mineral salts agar plate inoculated with Aspergillus niger spores.
• Incubate the plates in a constant temperature and humidity chamber at 28 degrees Celsius and over 90% humidity for 7 days.
• Regularly observe the specimens for fungal germination on the surface or the formation of a zone of inhibition (an area around the specimen where mold does not grow).

AATCC 30: Rating System and Passing Criteria

The results for AATCC 30 Test III are determined through a combination of macroscopic (naked eye) and microscopic observation. The criteria evaluate not only the cleanliness of the specimen surface but also the diffusion capability of the antifungal agent. The following is the standard industrial grading system:

Antifungal Rating Criteria:

• No Growth: No mold is visible on the specimen surface, even under a microscope. This is considered a “Pass.” A zone of inhibition indicates superior performance.
• Microscopic Growth: Mold spots are not visible to the naked eye but hyphae (fungal threads) are visible under 50x magnification. This is usually considered a “Fail.”
• Macroscopic Growth: Mold spots are clearly visible to the naked eye. This is a “Fail.”
• Zone of Inhibition: An area outside the specimen edge with no fungal growth. Typically, a zone wider than 1 mm indicates excellent antifungal performance.

ASTM E2149: Background and Technical Definition

ASTM E2149 is a quantitative standard for evaluating the antimicrobial activity of non-leaching agents under dynamic conditions. Titled “Standard Test Method for Determining the Antimicrobial Activity of Antimicrobial Agents Under Dynamic Contact Conditions,” it is specifically designed for antimicrobial fabrics where the active agent is permanently fixed to the fiber and does not migrate or wash away (e.g., silver ion or quaternary ammonium treatments). The technical principle involves mechanical agitation to force contact between bacteria and the antimicrobial sites on the fabric. It is the key technical evidence for “antibacterial and anti-odor” claims in sportswear, socks, and functional underwear.

ASTM E2149: Dynamic Contact Test Procedure

ASTM E2149 utilizes the unique “Shake Flask Method,” ensuring thorough contact between bacteria and the fabric through high-speed shaking. This method simulates the real-world process where bacteria in sweat flow through fabric fibers during physical activity. The core operation is as follows:

• Prepare a bacterial suspension of a specific concentration using Staphylococcus aureus or Escherichia coli.
• Cut 1 gram of the sample into small pieces and place them in a flask containing the bacterial suspension.
• Place the flask on a shaker and agitate at a high speed of 285 revolutions per minute for 1 hour.
• After shaking, take samples for culture and count the number of remaining viable bacteria.

ASTM E2149: Passing Criteria and Antimicrobial Rate Calculation

The determination for ASTM E2149 is based on the “Bacterial Reduction Rate.” The test compares the total bacterial count of the experimental sample and the untreated control sample after 1 hour of shaking to calculate the percentage of bacteria killed. The logic is: subtract the number of bacteria in the experimental sample from those in the control sample, then divide by the control sample’s count. Commercial passing standards typically require a reduction rate of 99% or 99.9% or higher. If the reduction is less than 50%, the fabric is considered to lack effective antimicrobial activity.

Core Differences Between AATCC 30 and ASTM E2149

In functional textile development, understanding the differences between these two standards is vital. The table below clearly illustrates their distinctions across various dimensions:

Dimension	AATCC 30 (Antifungal)	ASTM E2149 (Antimicrobial)
Target Organism	Fungi (e.g., Aspergillus niger, Chaetomium globosum).	Bacteria (e.g., S. aureus, E. coli).
Test Logic	Observes if fungi can “colonize” and grow on the fabric.	Calculates the number of bacteria killed upon contact.
Contact Method	Static contact/incubation.	Dynamic mechanical agitation/collision.
Industry Focus	Outdoor, geotextiles, warehousing, and shipping.	Sportswear, underwear, medical textiles.

Fabric Finishing Requirements and Process Suggestions

Developing high-quality fabrics that meet both standards requires precise control of the finishing process. Standard antibacterial agents often fail antifungal tests; therefore, specific process adjustments are necessary:

• Agent Specificity: Antifungal testing requires antifungal agents, while odor-control requires antibacterial agents. For comprehensive protection, a combined finish is recommended.
• Surface Tension Control: If excess residues or softeners remain on the fabric surface, they can coat the antimicrobial sites like a film, leading to ASTM E2149 test failure.
• Drying and Equilibrium: Antifungal tests are highly sensitive to moisture. Fabrics must be thoroughly dried after processing and allowed to reach equilibrium in a controlled environment before testing.
• Durability Performance: Since it is a dynamic contact test, the antimicrobial agent must be firmly bonded to the fiber; otherwise, the effect will rapidly diminish after several washes.

Common Technical Misconceptions Regarding These Standards

• Misconception 1: Antibacterial fabrics are also antifungal. Incorrect. Bacteria and fungi have completely different biological structures. Chemicals that kill Staphylococcus aureus may be entirely ineffective against the growth of Aspergillus niger.
• Misconception 2: A large zone of inhibition always means a better fabric. Incorrect. ASTM E2149 targets fixed agents, which typically do not produce a zone of inhibition, yet they can still achieve a 99.9% kill rate.
• Misconception 3: ASTM E2149 can test antiviral properties. Incorrect. This standard is for bacteria only. Viruses are much smaller and require evaluation via specific standards like ISO 18184.
• Misconception 4: Synthetic fibers do not need antifungal treatment. Incorrect. While polyester itself does not support mold, residues such as sizing, oils, and dirt on the fabric are ideal food sources for fungi.

FAQ: Frequently Asked Technical Questions