Many Protective Glasses Do Not Meet Specs for Shielding Light from Ultrafast Lasers

December 04, 2017

Many Protective Glasses Do Not Meet Specs for Shielding Light from Ultrafast Lasers 

High-power, ultrafast pulsed lasers increasingly supply light for biomedical applications and imaging, materials processing, industrial micromachining and more. But many laser eyewear products are not tested with ultrafast lasers and may not be providing adequate protection for the technical workers who depend on them.   

The main reason for this situation lies in the typical test procedures and standard measurements widely followed by eyewear makers to set their product specifications. Those methods use low-power, continuous light sources. As a result, they do not capture many potential hazards of actual high-power, pulsed-laser working conditions. Moreover, end users only infrequently test how their eyewear performs in particular applications prior to deployment.

Scientists at the National Institute of Standards and Technology (NIST) recently published a study of 24 samples of protective filters used in eyewear from five different manufacturers. They found that “some of them are good, but some did not perform even close to their own specs when used with ultrafast lasers,” said NIST researcher and study co-author Ted Heilweil.

In one case, a filter claiming a certain optical density (indicating the proportion of light it blocks) actually provided 10,000 times less light reduction than specified. Others blocked the specific wavelength for which they were rated, but transmitted much more light at nearby wavelengths. 

Why does this happen? The answer is in the nature of ultrafast pulsed lasers—those that emit light pulses with a duration measured in femtoseconds (fs, a millionth of a billionth of a second, 10-15 s). Unlike the more familiar “continuous-wave” lasers, or even pulsed lasers with longer pulses, whose output beams vary only in a very narrow range around a single center wavelength, high-speed laser pulses carry a much wider span of wavelengths. (See illustration.) As the pulses get shorter in time, the range gets wider.

Unlike continuous-wave lasers, which produce only one very narrow wavelength, ultrafast pulsed laser bursts contain light of many different wavelengths.

But eyewear manufacturers typically do not test their lenses against ultrafast pulsed lasers, or measure how much light they block at wavelengths near the rated wavelength. Indeed, some set their specifications without using laser light at all, relying on standard spectrometers with limited measurement capabilities.

So, the researchers, initially supported by NIST’s Office of Safety, Health and Environment, began to investigate how well the filters in protective eyewear performed in stopping light from femtosecond pulses. 

Each of the 24 plastic or glass filter samples was rated by its manufacturer to block light at a wavelength of 800 nanometers (nm, billionths of a meter, 10-9 m). The samples were tested at NIST using a generic ultrafast titanium:sapphire laser with a center wavelength of 800 nm―infrared light just below the threshold of human vision―running at 80 million pulses per second and producing pulses lasting about 40 fs.

Almost immediately, the NIST team and collaborators at Hood College in Frederick, Maryland, found “some pretty weird stuff,” Heilweil said. As expected, the pulses contained wavelengths ranging from 750 nm (visible red) to 900 nm (near infrared). Each filter responded differently to various sections of that span; one possible reason, the researchers speculate, is that the lenses may have different formulations of light-absorbing dyes.

For example, one filter that blocked much of the light at 800 nm blocked only one-hundredth as much at 847 nm. Many filters did not meet their own specs when the center wavelength was changed by only 1 percent. Some lenses were damaged by direct illumination in a few seconds, with results ranging from near transparency to complete opacity. And some performed extremely well across the entire range of wavelengths.

The new study is the first of many that are needed, Heilweil said. “It’s more like a startup point. We’ve just focused on one type of femtosecond laser. There are all different kinds, and tunable ones, too.”

Of course, the sorts of high-precision measurements conducted at NIST are not broadly available, and “it is impractical for laser eyewear manufacturers to establish their own femtosecond laser-based test facilities, which cover all possible output conditions of ultrafast systems,” Heilweil said. “So, we are trying to encourage manufacturers to use the best possible testing laboratories to evaluate their lenses.

“At the same time, and equally important, we need to get end users to be more aware of the precise wavelengths their lasers are producing. They need to test their eyewear themselves—in the specific conditions and particular applications for which they will be used—before putting them on,” said Heilweil.

Safe Baggage Handling Practices at Cruise Terminals

A recently released fact sheet from OSHA is intended to protect longshore workers who handle baggage at cruise ship terminals. 

Porters and baggage handlers frequently bend, kneel, crouch or crawl in unnatural positions while working, making them susceptible to injuries, the fact sheet states. The resource encourages employers to promote safe lifting techniques. Tips include:

  • Perform gentle range-of-motion exercises before shifts to warm up muscles.
  • Don’t assume an object’s weight based on its size; check for tags indicating heavy baggage and request help if an object is too heavy
  • Hold bags close and centered to your body while keeping a baggage cart or cage nearby to limit the lifting process
  • Lift slowly and steadily, using your legs instead of your back
  • Turn with your feet while lifting. Don’t twist your waist.
  • Don’t stack baggage above shoulder height
  • Use alternate routes if transporting baggage over slippery or uneven surfaces


The fact sheet also offers tips on using equipment, including carts, cages or forklifts:

  • Only use equipment in good working condition
  • Don’t deviate from instructions when operating mechanical equipment
  • Use restraining devices on cages, when necessary
  • Don’t stack bags too high
  • Practice extra caution when using pallet jacks to transport baggage
  • Follow established traffic patterns and be mindful of your surroundings


California to Adopt Exposure Levels for Hexamethylene Diisocyanate and Toluene

California’s Office of Environmental Health Hazard Assessment (OEHHA) has released two draft documents for public review, summarizing the toxicity and derivation of proposed Reference Exposure Levels (RELs) for Hexamethylene Diisocyanate (HDI) and toluene. RELs are airborne concentrations of a chemical that are not anticipated to result in adverse non–cancer health effects for specified exposure durations in the general population, including sensitive subpopulations.

OEHHA is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360(b)(2)).  In response to this statutory requirement, OEHHA develops RELs and inhalation cancer unit risk factors for many air pollutants.  The proposed HDI and toluene RELs were developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for the Derivation of Noncancer Reference Exposure Levels,” finalized by OEHHA in 2008.  

The draft HDI and toluene REL documents are available starting today on the OEHHA website.  The posting of the document will commence a 60-day public review period that will end on January 30, 2018. 

Public workshops will be held in Northern and Southern California at the following locations and times:

Northern California                            Southern California

January 8, 2018                                January 10, 2018
1:30 PM - 4:30 PM                            9:00 AM - 12:00 PM
Training Room 1 East                       Room CC-2
Cal/EPA Building                              South Coast Air Quality Management District
1001 I Street                                     21865 E. Copley Drive
Sacramento, CA 95812                     Diamond Bar, CA 91765 

After the close of the public comment period, the documents will be revised as appropriate by OEHHA, and peer reviewed by the state’s Scientific Review Panel on Toxic Air Contaminants. 

Comments on the documents, in writing or by e–mail, and any inquiries concerning technical matters or availability of the documents may be directed to:

Dr. John Budroe
Chief, Air Toxicology and Risk Assessment Section
Air, Community, and Environmental Research Branch
Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, CA, 94612
Telephone: 510-622-3145 

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the California Air Resources Board website at (link is external)

California’s Proposition 65 Rules Revised to Reflect Changes in TSCA

California’s Office of Administrative Law approved amendments to Title 27, California Code of Regulations, section 27000. The changes will be effective on January 1, 2018.  These amendments incorporate 2016 amendments to the federal Toxic Substances Control Act and make other non-substantive changes.  

The regulatory text and the supporting rulemaking documents are available at the following links:

Notice of Proposed Rulemaking

Initial Statement of Reasons

Final Statement of Reasons

Final Adopted Regulatory Text 

Questions regarding this rule change may be directed to Monet Vela, at or 916-323-2517.

Marshall Pottery, Inc. Settles with OSHA after Worker Death 

OSHA and Marshall Pottery, Inc., have reached a settlement agreement including a penalty of $545,160, after the death of an assistant plant manager.

On April 16, 2017, investigators determined that the manager was servicing a kiln and became trapped inside when it activated. The company was cited for six willful violations and 21 serious violations. Citations were issued following OSHA’s investigation into failures to implement confined space and lockout/tagout programs.

“This company was cited for similar violations in 2008 after another fatality at the plant,” said OSHA Area Director Basil Singh, in Dallas. “Failures to implement lockout/tagout and confined space programs are unacceptable. Employers must use all required safeguards and procedures to prevent the recurrence of similar tragedies.”

US Environmental Inc. to Pay Over $300,000 in Proposed Penalties for Safety Violations 

US Environmental Inc. has been cited by OSHA for 12 safety violations, including willfully exposing workers to confined space and fall hazards at its Downingtown location. The company faces proposed penalties of $333,756.

Investigators inspected the facility on May 31, 2017 and found that the company failed to implement rescue procedures for employees in confined spaces; provide protective equipment when working in confined spaces; and provide employees with fall protection training and equipment. OSHA cited the company for one other-than-serious, four willful, and seven serious violations.

“It is fortunate that workers did not suffer serious injuries or worse,” said OSHA Area Office Director Theresa Downs, based in Philadelphia. “Employers must follow appropriate atmospheric testing procedures, and provide adequate training and safety equipment to protect workers from potential confined space hazards.”

Manafort Brothers, Inc. Cited by OSHA for Mercury and Respirator Hazards at Demo Site

OSHA has cited Manafort Brothers, Inc. for exposing workers to mercury and respirator hazards while they dismantled a mercury boiler at a Portsmouth worksite. The Plainville, Connecticut, construction contractor faces penalties of $329,548.

OSHA’s inspection – in response to workers’ complaints – found that employees were being exposed to high levels of mercury during the demolition and Manafort Brothers Inc. was not taking steps to reduce those exposures to below permissible levels. In addition, the company did not evaluate the respirator program’s effectiveness in protecting workers against exposures and did not consult with the employees to identify and correct any respirator problems.

“These hazards were certainly preventable,” said OSHA’s New Hampshire Area Director Rosemarie O. Cole. “High mercury exposure can result in permanent nervous system and kidney damage. It is critically important that employers remain vigilant and ensure that effective safeguards are in place to prevent and minimize workers’ exposures.”

In total, OSHA cited the company for two willful and six serious violations concerning mercury, respirators, protective clothing, and sanitary conditions.

Companies Recognized for Outstanding Health, Safety and Environmental Performance 

The Vinyl Institute (VI) announced recipients of its annual health, safety and environmental awards, which are given to companies in the vinyl industry for improving worker safety and protecting the environment at facilities throughout the United States and Canada. This year the VI recognized 43 facilities for outstanding performance.

These awards are based on facility performance according to OSHA recordable incidents, the EPA National Emission Standards for Hazardous Air Pollutants (NESHAP), other regulatory permit performance, and the EPA's Toxic Release Inventory data for air and water during the 2016 calendar year.

"The Vinyl Institute members' commitment to continually improve in the areas of worker safety and environmental performance is the hallmark of our industry," said VI President and CEO, Richard Doyle. "Their focus on safety training, process improvements, and technological advancements have made the North American vinyl resin and monomer industry one of the safest manufacturing industries with an OSHA occupational injury and illness rate that is less than half the rate of the overall chemical industry and one fourth the rate of overall manufacturing. In addition, the vinyl industry has experienced an 83% reduction in unit vinyl chloride emissions while our industry's PVC resin production in the U.S. has increased by 91%."

Each year the Vinyl Institute proudly recognizes facilities in the vinyl and EDC/VCM categories that have achieved outstanding performance in four categories: Safety Excellence, Safety Performance, Environmental Excellence and Environmental Honor. For the second year, the VI included and recognized the health, safety, and environmental performance of companies with facilities involved in plasticizer production, additive production and PVC and chlorinated PVC compounding.

The Vinyl Institute's Safety Excellence Awards are based upon federal OSHA recordable incidents, which are defined as an occupational injury or illness resulting in medical treatment.  The awards, which recognize plants with five or more consecutive years with no recordable incidents, were presented to (in alphabetical order):

  • Eastman Chemical Company Plasticizer/Additive Manufacturing plant, Texas City, TX (5 consecutive years of performance)
  • ExxonMobil Chemical Company Plasticizer/Additive Manufacturing, Baton Rouge, LA (5 consecutive years of performance)
  • Formosa Plastics Corporation PVC Compounding plant, Point Comfort, TX (6 consecutive years of performance)
  • OxyChem EDC plant, Geismar, LA (6 consecutive years of performance)
  • Oxy Vinyls Canada PVC plant, Niagara Falls, Ontario (9 consecutive years of performance)
  • Westlake Vinyls PVC plant, Geismar, LA (7 consecutive years of performance)


Over $500,000 Fine for Death of Assistant Plant Manager for LOTO Violations

OSHA and Marshall Pottery, Inc., have reached a settlement agreement including a penalty of $545,160, after the death of an assistant plant manager.

On April 16, 2017, investigators determined that the manager was servicing a kiln and became trapped inside when it activated. The company was cited for six willful violations and 21 serious violations. Citations were issued following OSHA’s investigation into failures to implement confined space and lockout/tagout programs.

“This company was cited for similar violations in 2008 after another fatality at the plant,” said OSHA Area Director Basil Singh, in Dallas. “Failures to implement lockout/tagout and confined space programs are unacceptable. Employers must use all required safeguards and procedures to prevent the recurrence of similar tragedies.”

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