by The Durisol Team » Mon Nov 14, 2011 10:52 am
Hi:
The truth is offgassing of VOCs is a little more complicated than most people are willing to take the time to understand. We have attempted to be as technical as possible, while also describing the properties of Durisol in an accurate manner that shows the comparable difference and advantage of Durisol to other products.
In short, Durisol is free of off-gassing VOCs. The purpose of the table in the tech guide is to show the relative performance of Durisol. For example Durisol has 1/28th the offgassing as compared to polystyrene, 1/36th the offgassing as compared to conventional spruce lumber, and 1/3 the off gassing of concrete block. It is only comprised of cement and softwood. There are no other chemicals, binders or compounds in the material.
For the more detailed explanation, In terms of absolute numbers and the true affects of offgassing and indoor air quality, some factors that need to be considered are:
1. When the material is tested (as soon as it is manufactured, after it is installed in the home (pre-occupancy), post occupancy, etc.
2. The rate of decline in VOCs - does it take a day, a week, a year, etc for all of the gasses in the material to be released. This also depends on the initial inherent VOC content and rate at which the material can release the gasses. If a material is done off-gassing in a week and the material is not installed in a home until a month, then the initial VOC measure is fairly irrelevant in terms of indoor air quality.
3, The ability of the material to take on other VOCs from other materials. some materials can act as a sink and take on VOCs from the surroundings. For example in the test that we list in our tech guide, normal gypsum drywall obtained from a commercial outlet (Home Depot, etc) initially had VOCs measuring over 280 (micrograms per square metre per hour). It was concluded that high VOC value was because the drywall acted as a VOC sink and aborbed / adsorbed VOCs from nearby laminates, plywoods, etc. It also released the VOCs very quickly when removed from other sources of VOCs.
4. Other sources of VOCs related to installation and construction. For example in the test we quote, a normal concrete foundation wall resulted in VOCs measured at 2800 (micrograms per square metre per hour). This is more than 280 times that of Durisol. This high VOC was not from the concrete itself, but from the form release oils used in the wooden formwork to ensure that the forms can be removed from the concrete.
Historically, beginning in the 1970s, the National Aeronautics and Space Administration
(NASA) tested everything that went on board spacecraft to ensure the safety of the astronauts
and the protection of the technical equipment and spacecraft materials. In the early 1970s,
Danish researchers began testing composite wood products for formaldehyde and other
emissions believed responsible for occupant-reported irritation, odor perception, and illness in
buildings. Formaldehyde emissions from composite wood products used in manufactured
housing and mobile homes became a major focus for health and irritation effects complaints and
litigation in the late 1970s. In the early 1980s, a few organizations including Lawrence Berkeley
Laboratory (LBL) tested combustion appliances for emissions that might be life threatening or
capable of other, less serious health effects. It was recognized that reducing emissions could
reduce the need for dilution ventilation and, thereby, reduce building energy consumption, so
methods for testing emissions from building materials were developed. Shortly thereafter, EPA’s
Office of Research and Development (ORD) began its program developing methods for testing
emissions from building materials. That work eventually produced the first general ASTM
emission test guidance document, D5116-90, thenrevised as D5116-97. That document
formed the basis for European emissions test standards and is still regarded internationally as the
most important guidance document on emissions testing.
The tests listed in our tech guide are tests that were based on D5116-90 which is a small chamber test. Diluting and ventilation might be a problem in outer space, but not so much on earth.
Small chambers have obvious limitations. Normally, only samples of larger materials (for example, carpet) are tested. Small chambers are not applicable for testing complete assemblages (for example, furniture). Small chambers are also inappropriate for testing combustion devices (for example, kerosene heaters) or activities (for example, use of aerosol spray products). For some products, small chamber testing may provide only a portion of the emission profile of interest. For example, the rate of emissions from the application of high solvent materials (for example, paints and waxes) via brushing, spraying, rolling, etc. are generally higher than the rate during the drying process. Small chamber testing can not be used to evaluate the application phase of the coating process. Large (or full-scale) chambers may be more appropriate for many of these applications.
In practice, indoor air quality practitioners may use several different techniques for evaluating TVOC in buildings. Each sampling & analytical method has its own benefits and drawbacks, cost implications, and applicability. In short, the D5116-90 should be used as an relative indicater and should still be interpreted based on knowledge of actual in-situ conditions.
