Technology

Milestones in Mining Safety and Health Technology News NIOSH MINING SAFETY AND HEALTH RESEARCH

No. 556 January 2017 

The NIOSH LED Cap Lamp Provides Improved Illumination 

for Greater Safety in Underground Mines 

Figure 1: (Left) Illumination provided by an LED cap lamp in an underground mine. (Right) The improved illumination provided by the 

NIOSH-developed LED cap lamp. 

Photos by NIOSH 

Summary 

Researchers at the National Institute 

for Occupational Safety and Health 

(NIOSH) have developed an LED cap 

lamp that signifi cantly improves 

illumination in underground mines, 

thereby enhancing safety by reducing 

injuries to miners. Providing better 

illumination underground improves a 

miner’s ability to see and avoid potential hazards in the mine (see Figure 1). 

Results from NIOSH’s scientifi c testing 

confirm that the NIOSH LED cap lamp 

demonstrates major improvements 

in trip hazard detection, peripheral 

motion detection of moving hazards, 

and reduced glare when compared 

to existing LED cap lamps. The NIOSH 

LED cap lamp design is now freely 

available for commercialization by 

cap lamp manufacturers. 

By John J. Sammarco 

Background 

Providing adequate lighting for miners 

to work safely is a signifi cant challenge 

given that underground mines are one 

of the most diffi cult environments to 

illuminate. Illumination plays a critical 

role in an underground miner’s safety 

because miners depend most heavily on 

visual cues to see fall-of-ground hazards, pinning and striking hazards from 

powered machinery, and slipping and 

tripping hazards [Cornelius et al. 1998]. 

Accident rates can decrease signifi cantly when mine illumination is improved 

[Daly 2001]; researchers have noted that 

accident rates decrease as much as 60% 

when the overall illumination is increased 

[USBM 1988]. 

When illuminating an underground mine, 

age is an important factor to consider, 

given that the average age of the mining 

workforce is about 43 years [NIOSH 2012]. 

Age has a signifi cant effect on one’s visual abilities. The physiology of the human 

eye degrades as a person ages, resulting 

in decreased visual performance. These 

age-related changes include reduced 

pupil size, yellowing of the eye lens, loss 

of rod photoreceptors, and increased 

susceptibility to glare [Harvard Women’s 

Health Watch 2007]. Consequently, 40% 

less light reaches the retina of a 45-yearold person as compared to a 24-year-old 

[Rea 2000]. Thus, as the mining workforce 

ages, the need for eff ective underground 

lighting becomes even more pressing. 

Approach 

To improve the illumination capability 

of LED cap lamps, NIOSH conducted research in two phases. Phase I focused on 

enhancing the color of light to improve 

miners’ ability to see hazards, especially 

for older workers. NIOSH’s approach 

was to alter the color spectrum of the 

cap lamp to increase the output of short 
 

wavelength light. The short wavelength light emitted from a 

cool-white LED can improve visual acuity because the human 

eye is more sensitive to that part of the color spectrum in 

lowlight mining conditions. The alternative approach would 

be to increase the light intensity of the cap lamp. Although this 

would improve the ability to see hazards, the glare would also 

increase, and the battery would discharge faster. 

Phase II of the research focused on changing the distribution 

of light to increase visibility of the mine floor and of moving 

machinery. A single light source, along with a reflector to direct 

light to a circular spot, provides the typical lighting distribution from an LED cap lamp (see Figure 1, Left). This spot beam 

creates a tunnel vision effect that limits peripheral visibility 

of moving machinery. With this in mind, NIOSH designed a 

Figure 2: The NIOSH LED cap lamp uses multiple LEDs as the primary 

light source for better illumination distribution. 

cap lamp using multiple LEDs as the primary light source (see 

Figure 2), along with secondary totally internal refl ection optics 

that distribute the light to specific hazardous areas within the 

mine (see Figure 1, Right). The cap lamp beam distribution and 

intensity are software controlled, enabling the fl exibility of 

matching the cap lamp lighting to the worker’s task via a pushbutton selection of various lighting modes (see Figure 3). 

Reported Findings 

The Phase I results of enhancing the color of light to improve 

visual performance indicated significant improvements for 

people 50 or more years old. Peripheral motion detection improved by 15%, floor trip hazard detection improved by 23.7%, 

discomfort glare was reduced by 45%, and disability glare was 

reduced by 53.8% [Sammarco et al. 2010]. The Phase II results 

indicated a 94% faster detection rate of trip hazards and a 79% 

faster detection rate of peripheral motion, with no increase in 

glare [Reyes et al. 2011]. 

Figure 3: The NIOSH LED cap lamp’s beam distribution and intensity 

can be selected for various lighting needs. 

Photo by NIOSH 

References 

Cornelius K, Steiner L, Turin F [1998]. Using coal miners’ experience to identify effective operating cues. 42nd Annual Meeting 

of the Human Factors and Ergonomics Society, http://www. 

cdc.gov/niosh/mining/works/coversheet1371.html.

Daly C [2001]. Close aspect lighting in underground coal mines. 

Report No. C7032. Australian Coal Association Research Program. 

Harvard Women’s Health Watch [2007]. Blinded by the night. 

Harvard Health Publications, June, http://www.health.harvard. 

edu/diseases-and-conditions/blinded-by-the-night. 

NIOSH [2012]. National survey of the mining population. Part 

I: employees. By McWilliams LJ, Lenart PJ, Lancaster JL, Zeiner 

JR Jr. Pittsburgh, PA: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, DHHS (NIOSH) 

Publication No. 2012–152. 

Rea MS, ed. [2000]. The IESNA lighting handbook: reference & 

application. 9th ed. New York: Illuminating Engineering Society 

of North America. 

Reyes M, Sammarco J, Gallagher S, Srednicki J [2011]. Comparative evaluation of light emitting diode cap lamps with an emphasis on visual performance in mesopic lighting conditions. 

In: Proceedings of the IEEE Industry Applications Society 44th 

Annual Meeting. Orlando, FL. October 2011, http://ieeexplore. 

ieee.org/stamp/stamp.jsp?arnumber=6074389. 

Sammarco J, Gallagher S, Reyes M [2010]. Visual performance 

for trip hazard detection when using incandescent and LED 

miner cap lamps. J Safety Res 41(2):85–91. 

USBM [1988]. Human factors in mining. By Sanders MS, Peay 

JM. Pittsburgh, PA: U.S. Department of the Interior, U.S. Bureau 

of Mines. IC 9182, http://www.mirmgate.com.au/docs/Ergonomics_References/Human_Factors_In_Mining_ic9182.pdf. 

Photo by NIOSH 

For More Information 

For more information on the NIOSH LED cap lamp, contact John J. Sammarco (jsammarco@cdc.gov), or the NIOSH Mining program 

(mining@cdc.gov). The NIOSH LED cap lamp design can be downloaded at: http://go.usa.gov/xKeRG. 

To receive NIOSH documents or for more information about occupational safety and health topics, 

contact: 1-800-CDC-INFO (1-800-232-4636), 1-888-232-6348 (TTY), or request information at the 

CDC website at www.cdc.gov/info, or visit the NIOSH website at www.cdc.gov/niosh. 

DHHS (NIOSH) Publication No. 2017–119