If the cans are the same size, are the contents the same?
Illustration: It can be hard to determine from the exterior of the container (left), but contents may be either mixed with the propellant (center) or confined in a bag (right).
The work of NIST can be found in many unexpected places in American life -- including store shelves containing different kinds of aerosol products. So perhaps it's not surprising that PML's Office of Weights and Measures (OWM) was called upon to help resolve a dispute over the way such products are labeled and sold.
Many familiar aerosol products contain a mixture of the active ingredient and the propellant gas. Both are expelled at the same time. But in "bag-on-valve" (BOV) containers – which are used for a range of products including sunblock sprays, deodorants, window cleaners, insecticides, furniture polish, and automotive lubricants – the active ingredient is confined in a sealed bag within the can, surrounded by pressurized gas.
The issue was that while standard aerosols are sold by weight, the BOV containers were sold based on fluid volume. Because these products are not easily distinguished on a store shelf, the competing sale methods make consumer value comparisons difficult, if not impossible.
Seeking consensus, a team from OWM hosted a meeting of representatives from various aerosol industry groups, trade associations, and federal agencies. After multiple presentations and a thorough discussion, they reached a unanimous agreement that the products should be sold by weight. The resulting report will help guide future regulation and industry standards.
"It's as fair as it can be," says David Sefcik of OWM. "The BOV companies won't have to distinguish themselves from aerosols. And consumers will be able to make rational purchasing decisions and value comparisons based on a common method of sale."