The Modified Dust Trap (MDT) test measures how well a breathable fabric, seam or zip stops dust mite and cat allergen while air passes through it. House dust carrying a known amount of allergen is drawn across the sample under controlled airflow. A filter behind the sample catches whatever gets through, and allergen-specific ELISA measures it. One test gives you both barrier performance and airflow.
The method was developed by Professor Thomas Platts-Mills’s group at the University of Virginia and published in the Journal of Allergy and Clinical Immunology in 1999. Airmid Healthgroup runs an adapted version as its Allergen Barrier Test with Airflow (method SP304) for bedding, encasings, upholstery fabrics, vacuum cleaner bags and filter media.
- Also known as
- Modified Dust Trap (MDT) test · Allergen Barrier Test with Airflow · Airmid method SP304
- What it measures
- Allergen passing through the sample (ng), filtration efficiency (%) and airflow (L/min)
- Allergens
- Der p 1 (house dust mite) and Fel d 1 (cat)
- Analysis
- Allergen-specific ELISA. Airmid is INAB accredited (Reg. No. 284T) for Der p 1 and Fel d 1 ELISA; the SP304 test procedure itself is outside the accreditation scope.
- Limits of detection
- 4 ng Der p 1 · 2 ng Fel d 1
- Controls
- A positive reference fabric and a 100%-blocking negative control in every test
- Materials
- Polyester, cotton, poly-cotton and microfibre fabrics, prototypes, seams, cross seams and zips, vacuum cleaner bags and appliance filter media
- Sample and turnaround
- 1 m² of fabric · 15 working days from sample receipt
Where the Modified Dust Trap test comes from
By the late 1990s, mattress and pillow encasings were standard advice for people allergic to house dust mite. Many of the encasings on the market blocked allergen and let water vapour through, but did not let air pass freely through the material, which made them uncomfortable to sleep on. Manufacturers began offering breathable alternatives made from tightly woven or nonwoven synthetic fibres, and there was no reliable way to check whether those fabrics held back allergen.
John Vaughan, Thomas Platts-Mills and colleagues at the University of Virginia Asthma and Allergic Diseases Center set out to build that test. They started with a commercial vacuum dust trap supplied by Fussnecker, a vacuum cleaner specialist in Springfield, Ohio, and modified it so that sieved house dust could be pulled onto and through a fabric sample. An ordinary 1.1 horsepower vacuum cleaner provided the suction. A 37 mm filter downstream of the fabric collected any allergen that got through, and the team recorded the airflow and the pressure drop across each fabric. The filters were then assayed for Der p 1, Der f 1 and Fel d 1 by two-site monoclonal antibody ELISA. The modified trap gave the method its name.
Professor Thomas A. E. Platts-Mills FRS is a leading figure in indoor allergen research. His group carried out the early purification of house dust mite allergen and developed immunoassays to measure it, work that shaped much of today’s advice on allergen avoidance and bedding encasings. In 2010 he became the first allergist elected a Fellow of the Royal Society.
What the 1999 study found
The study also showed the trade-off every barrier fabric has to manage: as average pore size fell, airflow through the fabric dropped and the pressure differential across it rose. The authors concluded that the method provided “a rigorous and reliable test for leakage of common indoor allergens through breathable barrier fabrics”.1
Later in 1999 the same group used the modified dust trap to test vacuum cleaner bags, pulling sieved house dust containing a known amount of Fel d 1 across the bag material. Single-layer bags let through far more cat allergen than most two- and three-layer microfiltration bags.2
How Airmid has developed the method
Airmid’s Allergen Barrier Test with Airflow (SP304) keeps the principle of the original modified dust trap: a measured allergen challenge, drawn through the sample by air, caught on a downstream filter and quantified by ELISA. We have added the controls and reporting that product claims need:
- A controlled challenge. House dust with a known concentration of Der p 1 and Fel d 1, drawn across the sample under regulated air pressure.
- Two controls in every test. A routinely used reference fabric (positive control) that results are benchmarked against, and a 100%-blocking barrier (negative control) that confirms nothing has contaminated the procedure. Both are used to calibrate the airflow device before testing starts.
- Accredited allergen analysis. Der p 1 and Fel d 1 ELISA within our INAB accreditation, with defined limits of detection, in our accredited allergen laboratory.
- Airflow on every sample. Reported in L/min, so barrier and breathability claims come from the same data.
- More than flat fabric. Seams, cross seams and zips, as well as vacuum cleaner bags and appliance filter media, and prototype fabrics made from novel components.
How the test works
- Calibrate. The airflow device is calibrated with the positive and negative control fabrics.
- Mount. The test fabric, seam or zip is clamped across the air path of the trap.
- Challenge. House dust with a known Der p 1 and Fel d 1 load is introduced upstream and drawn onto and through the sample under regulated air pressure. Airflow through the sample is recorded.
- Capture. Any allergen that passes through the sample is caught on a filter downstream.
- Measure. The filter is extracted and the allergen is quantified by allergen-specific ELISA.
- Report. You receive allergen recovered (ng), filtration efficiency relative to the positive control (%) and airflow (L/min).
What your report shows
| Result | Unit | What it tells you |
|---|---|---|
| Allergen recovered | ng | Total allergen that passed through the sample onto the downstream filter |
| Filtration efficiency | % | How much allergen passage the sample prevented, relative to the positive control fabric |
| Airflow | L/min | How freely air moves through the material, an indicator of breathability and comfort |
Results at or below the limits of detection (4 ng Der p 1, 2 ng Fel d 1) represent complete or near-complete allergen barrier performance. More detail on controls, units and detection limits is in our Allergen Barrier Test FAQ article.
Why measure allergen directly instead of pore size or thread count
Pore size and thread count are the most common shorthand for barrier performance, but they only loosely predict it. An average pore size hides the variation across a fabric, bubble-point methods cannot account for pores that do not open during measurement, and thread count says nothing about nonwovens. Van der Waals forces and the conformation of the allergen also affect whether a particle gets through, independently of pore geometry.
Particle size matters too. Dust mite allergen is carried mostly on faecal particles of roughly 10–40 µm, while cat allergen travels on much smaller particles, many under 10 µm. A fabric that stops mite allergen will not necessarily stop cat allergen, which is what the 1999 study found.
Airflow matters because a barrier nobody wants to sleep under does not help anyone. Poor breathability affects comfort, and comfort affects whether people with allergies keep using the product. The MDT test captures barrier performance and airflow in the same run.
How it compares with other ways of assessing barrier fabrics
| Approach | What it tells you | What it misses |
|---|---|---|
| Pore size (e.g. bubble point) | Average pore geometry | Variation across the fabric and unopened pores; no allergen data |
| Thread count | Weave density of woven fabrics | Not meaningful for nonwovens; no allergen data |
| Air permeability alone | How breathable the fabric is | Whether it blocks allergen |
| Live mite penetration (e.g. Siriraj chamber method3) | Whether live mites can pass through | Allergen-carrying particles are far smaller than the mites themselves |
| Modified Dust Trap (SP304) | Allergen passing through under airflow, plus airflow | Mechanical stress from everyday use |
| Simulated Use test (SP305) | Allergen transfer under the pressure and movement of use | Airflow and breathability |
The two Airmid methods complement each other. SP305 places the material between two chambers, one holding allergen-laden house dust and steel bearings, and rotates them for 20 hours at 25 RPM to simulate the pressure of normal use. For mattress and pillow encasings, running both gives a fuller picture than either alone. Where thermal comfort claims matter, breathability testing to ISO 11092 adds thermal and water-vapour resistance data.
Who uses the test
- Mattress, pillow and duvet encasing manufacturers
- Bedding and home textile brands making allergen barrier claims
- Upholstery and curtain fabric developers
- Fibre and fabric producers developing new barrier materials, including prototypes
- Vacuum cleaner bag and appliance filter manufacturers
We routinely test polyester, cotton, poly-cotton and microfibre fabrics. There is no universally best fabric type for allergen barrier performance, which is why each material needs testing on its own merits.
Results support allergen barrier claims on labels and packaging. Airmid testing data is recognised by the Asthma & Allergy Friendly® Certification Program and can be used in certification applications for bedding, mattress covers and other textiles. Our claims verification services can help you match the testing to the claims you plan to make.
Ordering a test
- Sample: 1 m² of each fabric. Tell us if you want seams, cross seams or zips assessed and we will advise on sample construction.
- Turnaround: 15 working days from sample receipt.
- Allergens: Der p 1 and Fel d 1 as standard.
Frequently asked questions
What is the Modified Dust Trap test?
The Modified Dust Trap test is a laboratory method that measures how much dust mite and cat allergen passes through a fabric, seam or zip while air is drawn through it. A measured allergen challenge is pulled across the sample, a downstream filter catches what gets through, and ELISA quantifies it. Airflow is recorded at the same time.
Who developed the Modified Dust Trap method?
John Vaughan, Thomas Platts-Mills and colleagues at the University of Virginia Asthma and Allergic Diseases Center developed the method and published it in the Journal of Allergy and Clinical Immunology in 1999. They built it from a commercial vacuum dust trap supplied by Fussnecker of Springfield, Ohio.
Is the Modified Dust Trap test the same as the Allergen Barrier Test with Airflow?
Yes. Allergen Barrier Test with Airflow is the name for Airmid Healthgroup’s adapted version of the modified dust trap method, run as test method SP304.
What pore size blocks dust mite and cat allergen?
In the original 1999 study, fabrics with an average pore size below 10 µm blocked dust mite allergen to below detectable limits, and cat allergen needed an average pore size of 6 µm or less. Pore size only loosely predicts real-world performance, so allergen barrier claims should rest on direct allergen testing.
How is the Modified Dust Trap test different from the Simulated Use test (SP305)?
The Modified Dust Trap test (SP304) draws allergen through the material by airflow and also measures breathability. The Simulated Use test (SP305) measures allergen transfer under mechanical stress: the material sits between two chambers that rotate for 20 hours with allergen-laden dust and steel bearings. Encasings benefit from both.
Can you test zips and seams?
Yes. Seams, cross seams and zips can be tested as well as flat fabric. This matters because an encasing is only as good as its weakest point.
Can Modified Dust Trap results support Asthma & Allergy Friendly® certification?
Airmid testing data is recognised by the Asthma & Allergy Friendly® Certification Program and can be used in certification applications for bedding, mattress covers and other textiles. The certification program sets the requirements for each product category.
How much sample do you need and how long does the test take?
We need 1 m² of each fabric. Standard turnaround is 15 working days from sample receipt.
References
- Vaughan JW, McLaughlin TE, Perzanowski MS, Platts-Mills TAE. Evaluation of materials used for bedding encasement: effect of pore size in blocking cat and dust mite allergen. J Allergy Clin Immunol. 1999;103(2):227–231. doi:10.1016/S0091-6749(99)70495-1
- Vaughan JW, Woodfolk JA, Platts-Mills TAE. Assessment of vacuum cleaners and vacuum cleaner bags recommended for allergic subjects. J Allergy Clin Immunol. 1999;104(5):1079–1083. doi:10.1016/S0091-6749(99)70092-8
- Mahakittikun V, et al. Mite penetration of different types of material claimed as mite proof by the Siriraj chamber method. J Allergy Clin Immunol. 2006. PubMed 17088144
Need allergen barrier data for a fabric, encasing or filter?
Talk to our team about the Modified Dust Trap test, the Simulated Use test, or a combined programme for your product claims.
