Manufacturer-stated · FluoroSpec on painted substrates

Limit of detection.

FluoroSpec can identify low levels of lead-based and lead-containing paint.

Manufacturer-stated limit of detection

Roughly 400 ppm by mass, or 0.1 mg/cm² by area, in normal indoor light, on common painted substrates. Below that the reaction can still occur, but the green signal can be faint enough that substrate color, paint binder, film thickness, and ambient light start to matter.

[ 01 ]The line the law draws.

Lead-based paint was banned from residential homes in 1978. From 1978 to 2008, the federal limit for lead-containing paint sat at 600 ppm. In 2008, the children's-product limit dropped to 90 ppm. The EPA definition of lead-based paint in housing has long sat at 5,000 ppm by mass, or 1.0 mg/cm² by area.

Anything below those thresholds is properly called lead-containing paint. Not lead-based paint. Still toxic. Still chips into dust. Still ends up in kids. The 5,000 / 1.0 line is an abatement threshold, not a safety threshold.

For perspective: actual old white lead-carbonate paint runs north of 400,000 ppm. The regulatory cutoff is already roughly two orders of magnitude below that.

[ 02 ]How it works.

FluoroSpec creates millions of tiny crystals on contact with lead. The crystals act like fluorescent mirrors, shining back the invisible UV light as visible green. The amount of lead tracks with the amount of light that comes off the surface.

[ 03 ]An example.

Using a vintage paint swatch booklet from Sherwin-Williams titled Color Harmony Guide, Centennial Edition, published in 1968, we gained access to real-life paint samples. Here are two to illustrate the above points.

1968 Sherwin-Williams Color Harmony Guide open to the olive hues page, source of sample A
Olive hues · sample A came from page 122
1968 Sherwin-Williams Color Harmony Guide open to the yellow hues page, source of sample B
Yellow hues · sample B came from page 156

Sample A · olive page 122

372ppm Pb

Reaction · 7s

XRF mass mode 372 ppm Pb ±5
XRF area mode 0.06 mg/cm² ±0.01
Status lead-containing paint
vs. LBP cutoff 13× below mass · 17× below area
XRF mass mode reading: 372 ppm Pb on olive page 122
372 ppm · mass mode
XRF area mode reading: 0.06 mg/cm² Pb on olive page 122
0.06 mg/cm² · area mode

Sample B · yellow page 156

1,058ppm Pb

Reaction · 9s

XRF mass mode 1,058 ppm Pb ±36
XRF area mode 0.09 mg/cm² ±0.01
Status lead-containing paint
vs. LBP cutoff 4.7× below mass · 11× below area
XRF mass mode reading: 1058 ppm Pb on yellow page 156
1,058 ppm · mass mode
XRF area mode reading: 0.09 mg/cm² Pb on yellow page 156
0.09 mg/cm² · area mode

Both samples reacted. The brighter, more concentrated ring on sample B is what 1,000+ ppm looks like to the eye. Sample A at 372 ppm reacts as dispersed flecks, the kind of signal that depends on substrate and lighting at the edge of detection.

[ 04 ]Honest limits.

  • Parts per million in a thin paint film is hard to derive without weighing the chip. XRF approximates it by depth-correcting; reading conditions matter.
  • FluoroSpec does not quantify. It locates. The green signal tells you lead is there, not exactly how much.
  • Reaction visibility depends on the substrate behind the paint, the paint binder, the film thickness, and the lighting at the read.
  • Near the limit of detection these factors are the difference between an obvious glow and a faint one.

Contact Eric Ritter for more information. To learn about lead-based paint dust detection, click here.