X-ray fluorescence (XRF) is an analytical method using emission spectroscopy to identify the presence of specific elements in most materials. Every element has a unique emission signature, making it possible to quantify the presence of an element by the relative strength of the emission. Instrumentation has evolved to the point where hand-held XRF can be used in the field for on-site testing purposes. While X-ray fluorescence is a very accurate and reliable instrumentation-based method for quantitative analysis of chemical elements, it should not be used as the sole identifier of toxic or Chinese drywall. To identify problem drywall, XRF is used to target the alkali earth element, strontium, as the primary identifier of problem drywall. There is no doubt the XRF will determine the accurate level of strontium in the wall section being scanned. However, there are several chemistry-related considerations that should force us to take a closer look at using only strontium content as the flag for identification of problem drywall.
What is Strontium?
- Strontium frequently replaces lead as a paint drier.
- Strontium is used in yellow, blue, red and white pigments.
- Strontium aluminate is used in glow-in-the-dark coatings, wallpapers and adhesive stickers.
- Strontium chromate, borate and metaborate are also used in anti-corrosion additives, flame retardants, and anti-microbial agents in paints and coatings. Therefore, it is conceivable that XRF readings for strontium could vary from room to room and even from wall to wall due to differing layers of paint.
- is naturally present in the drywall core;
- is commonly present in wall paints; and
- is NOT the proven source of the corrosive gasses.
To use the XRF method as a stand-alone tool to positively identify problem drywall makes no more sense than to use an X-ray machine as a stand-alone instrument to diagnose cancer. There is no basis in science or experience to support its use as a stand-alone method. There is a basis in science and experience to support the use of XRF as a highly reliable screening method for identifying suspect or problem drywall.
While the XRF method is both fast and non-destructive, it should only be used in concert with complementary problem drywall-testing protocols and trained visual inspection. It is clear that the real benefit of the XRF method is as a very efficient and highly reliable, non-destructive screening tool.