Using 3D printers and movie modeling techniques, UAB researchers enhance workplace safety devices

Claudiu Lungu and a team from UAB's Department of Environmental Health Sciences have devised a high-tech, low-cost method for designing and fabricating new respirator prototypes to improve workplace safety.

If you work on an auto painting crew, stir vats of artificial butter at a popcorn factory or handle asbestos at a shipyard, you are one of the 5 million American workers legally required to wear respiratory protective equipment on the job.

But legal requirements and actual practice don't always match up. And even when workers wear their respirators, they may not be doing much good.

Studies show that hundreds of thousands of workers—from 15 to 20 percent, according to recent research—may be wearing ill-fitting respirators, not designed for a workforce that has rapidly changed over the past decades.

But a UAB research team has devised a high-tech, low-cost method for designing and fabricating new respirator prototypes to better match the variety of facial shapes in today's workplace. In addition to protecting industrial workers, the technology could aid members of the military as well. The findings are published online in the Journal of Occupational and Environmental Hygiene.

One Size Doesn't Fit All

"This is a big issue, because if something doesn't fit well, people won't wear it," says Claudiu T. Lungu, Ph.D., associate professor in the Department of Environmental Health Sciences in the UAB School of Public Health, who is the corresponding author on the new paper. "They use it for awhile and then take it off." Even if the worker keeps the respirator on, "it's not like wearing it at all if you don't have a good fit," Lungu explains.

All respirators currently on the market are based on facial anthropometric measurements of U.S. Air Force personnel taken in the 1960s — when the test subjects, like the U.S. workforce, were largely white and male. "The workforce has changed dramatically in the past 10 to 20 years," Lungu says. "We've definitely seen more women working in professions that had been typically occupied by men. We've also seen a rise in ethnic diversity in the workforce."

Despite those changes, respirators today still "come in three sizes: small, medium and large," Lungu says. "Obviously human faces have greater variety than that."

The prototypes created by the UAB team will allow researchers to document the protective abilities of currently available respirators on various facial shapes—and test the protective prowess of new respirator models. 

Face Off

In a 2007 study, the National Institute of Occupational Safety and Health (NIOSH) took detailed measurements from both men and women, as well as members of different ethnic groups. "They discovered that about 15 to 20 percent of the working population is not fitted by any of the current respirators on the market," says Lungu.

NIOSH's new "fit panel" includes two new sizes: short/wide and long/narrow. A 2010 NIOSH study provided digital headform models sized to correspond with the new fit panel for use in respirator design and testing. But several years later, these changes in respirator sizing have yet to reach the marketplace. This can be accounted for in part due to the fact that the only physical versions of the headforms available are a set of rigid plastic prototypes at Texas Tech University.

One obstacle to wider adoption is the lack of research documenting a strong safety advantage for the new headform models. Without that data, manufacturers have little incentive to retool their production lines. That's where the UAB team came in.

In a series of studies, Lungu and doctoral student Paula S. Joe, along with collaborators Phillip Shum and David Brown in the Department of Mechanical Engineering, have made important advances in the field.

Making a New Mask

In a 2012 paper, the UAB researchers demonstrated that a relatively low-tech laser scanner can take accurate measurements of the human face, replicating the current standard method of manual measurement at far lower cost than the expensive 3D scanners used by NIOSH.

That same year, they used the plastic headform prototypes from Texas Tech to cast and mold silicone versions that much more accurately mimic the properties of human skin. Those silicone headforms allowed them to do preliminary fit testing on commercially available respirators.

In the latest study, the UAB team used a CT scanner in the UAB Department of Radiology, a 3D printer in Atlanta, and mask-making techniques borrowed from Hollywood special effects teams to create a respirator to accommodate the Short/Wide headform.

A CT scan of a currently available respirator facepiece gave the team the data to create their own version, sized to fit the image of the Short/Wide headform in a computer. They used the 3D printer to create a mold in hard plastic, then sculpted their respirator using silicone modeling techniques adapted from ones that Hollywood special effects artists use to create props for the movies.

"The advantage of our method is that it's really inexpensive, a fraction of the cost of 3D printing respirators" directly in silicone, Lungu says. "Flexible materials are currently extremely expensive for 3D printing, but that's the future. The ideal would be to do very fast 3D scans of the human face and then 3D print respirators for each individual who needs one. Then again, it's not going to happen in the next 10 years, or even probably the next 20 years. In the meantime, the method we have developed has great potential."

The next step for the UAB team is to fit-test their five custom-created headforms and respirator facepieces together. If the new facepieces perform better than currently available commercial respirators, the researchers plan to move forward with tests using a small sample of human participants.

"The same techniques can be applied to creating helmets, eye protection and a wide range of other safety devices," Lungu adds.