Technical
ASTM D3273-00
Information
Frequently Asked Questions
What is ASTM D3273-00? ASTM D3273-00 measures an interior coating鈥檚 resistance to mould growth in a severe interior environment.
Its official designation is Standard Test Method for Resistance to Growth of Mould on the Surface of Interior Coatings
in an Environmental Chamber.
In this standard test method, the interior coating being evaluated for mould resistance is applied to a 75 mm x 100 mm
(3 x 4 ) panel. One or more of these panels are then suspended over a non-sterile dirt bed that has been inoculated
with three specific types of mould spores.The test panels are kept in an environmental condition of 95%-98% relative
humidity and 32 掳C (90 掳F) for four weeks. Each week the samples are visually examined for mould growth.
The test results are reported using a scale of zero to ten, with ten representing no mould growth on the surface
of the coating. There is a separate test method used for rating the panels for mould growth. This test method is
ASTM D3274-95 鈥淪tandard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by
Microbial (Fungal or Algal) Growth or Soil and Dirt Accumulation.鈥?
What are some of the assumptions It was not designed for testing other building materials or systems.
1. The test is designed for interior coatings.
you must understand when using In fact, the test method precludes the use of this test for exterior coatings, stating 鈥溾?se of this test method for
ASTM D3273-00 to evaluate evaluating exterior coatings鈥? performance has not been validated鈥?. Should this test method be used for testing
building materials? an exterior coating system, a precautionary statement regarding interpretation of results as being outside the
scope of this test method must be included.鈥? This means that interpreting test results to represent definitive
installed performance in specific project conditions would be an error for exterior coatings. It would also be
incorrect to directly relate other building material test results to installed performance.
The test is not representative of installed performance of building systems. Suspending a small 75 mm x 100 mm
2.
(3 x 4 ) sample over dirt does not accurately relate to installed building system performance relative to mould growth.
The samples are exposed to three specific types of spores in controlled conditions, which certainly does not mirror
many job conditions.Therefore, the numbers that are obtained with this test method cannot predict how long a
building material would be free from mould growth in its installed condition.
There are over 100,000 known species of mould that occur naturally in the environment. ASTM D3273-00 uses three
3.
predetermined species. This typically is not representative of the species commonly found in buildings. Again,
results obtained with this test method cannot precisely predict how long a building material will resist growth.
The test influences building system performance. As mould develops on a test panel, it influences the airborne spore
4.
concentration within the test chamber. Test panels therefore influence the performance of their neighbors by
altering the exposure conditions to which the samples are subjected.
Rating is ambiguous. The test method assigns a numeric scale to the amount of mould growth but also states,
5.
鈥溾?erformance at a certain rating does not imply any specific period of time for a fungal-free coating.鈥?
Why is ASTM D3273-00 used Currently there are not any relevant alternatives. To date, it is one of two protocols to test materials for mould growth
to evaluate building materials? resistance that have an ASTM designation. The other method, ASTM G-21, Standard Practice for Determining
Resistance of Synthetic Polymeric Materials to Fungi, requires the material be actually placed in an agar (nutrient)
solution. While these test methods are appropriate for the products they are intended to represent, they have
inherent shortcomings when used to test other building materials. CGC is actively working with external experts
to develop a more meaningful test protocol for specific building materials.
What is the key to reducing The key to mould growth prevention is controlling moisture. Controlling moisture is a systems issue that must include
the risk of mould growth? consideration of the building design and construction practices. Moisture exposure can occur during construction
and through the building life cycle from condensation, roof and pipe leaks, gross water penetration of the fa莽ade,
and natural disasters. Products alone cannot control moisture or prevent mould. All products become susceptible to
mould growth under the right set of conditions. Moisture must be controlled in the system to prevent mould
growth. The USEPA has noted that mould will grow on stainless steel, glass and all surfaces, given the right
conditions.
Additional Information 鈥? Moisture Control System
For more information regard- Performance (EWB-W111)
ing moisture control, mould 鈥? SHEETROCK庐 Brand HUMITEK鈩?
and mildew, please refer to Gypsum Panels Submittal
the following literature: Sheet (EWB-W109)
鈥? The CGC Construction 鈥? Good Construction Practices
Handbook (EWB-W106)
鈥? Moisture, Mould, Mildew and 鈥? Storage and Handling 鈥?
Construction Practices Wallboard and Other
(EWB-0W95) Products (EWB-W108)
鈥? Moisture, Mould, Mildew and
Construction Practices 鈥?
Frequently Asked Questions
(EWB-0W96)
鈥? CGC Leadership brochure
(EWB-W110)
CGC Inc. www.cgcinc.com EWB-W107/4-03
漏2003, CGC Inc. CP
350 Burnhamthorpe Rd., W., 5th Fl.
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