This item can only be shipped to schools, museums and science centers
For the science teacher concerned about the presence of mercury vapor, this is a great first step for peace of mind on this issue. A 3" × 4¼" card has a piece of filter paper sandwiched in its center. The filter paper has been treated with palladium chloride, and its surface appears to be pink/tan in color. Upon exposure to mercury vapor, a color change occurs and the filter paper turns dark gray. The color change is sharp and distinguishable. You will want to hang this indicator/detector in your laboratory as an additional protection against mercury vapor. Sampling time is 10–14 days. This is not an instantaneous read-out device. Simply watch for a color change, which alerts you to possible problems.