martes, 16 de julio de 2013

CDC - NIOSH Science Blog – First NIOSH Comic Helps Dispel Internet “Myth”

CDC - NIOSH Science Blog – First NIOSH Comic Helps Dispel Internet “Myth”

First NIOSH Comic Helps Dispel Internet “Myth”

Categories: Construction

In June, we released the first-ever NIOSH comic Straight Talk About Nail Gun Safety. The comic has been well received by organizations and stakeholders  interested in increasing awareness and prevention of injuries resulting from nail gun use.  In the publication we described (p 1, panel 3) the pneumatic nail gun (PNG) velocity, 150 ft/sec, at the upper end of the range reported by two investigations that conducted tests to measure pneumatic nail gun velocity – the Consumer Product Safety Commission[1]  and the late Boulter Kelsey[2], a forensic engineer.  We received an inquiry  suggesting that 150 ft/sec understates the power of these tools and referenced a velocity nearly 10 times higher (1400 ft/sec).  We were confident in our data and knew that even at lower velocities, nail guns can cause serious injury, but we were curious:  How could such widely varying data exist in the scientific literature?  We were on the case. 
Initially, we were directed  to an article published on the “How Stuff Works” External Web Site Iconweb site entry about nail guns (How Nail Guns Work) which stated:  “Just like a handgun, power nailers fire projectiles at high speed — some designs launch nails at speeds reaching 1,400 feet per second (427 meters per second).” [3] No citation was provided for the velocity value.
When we turned to Google to find the original source, we ended up with 21,000 ‘hits’ by using “nail gun” and “1400 feet per second” as search terms.  Most sites that appeared immediately were legal or medical, though they quickly digressed to include ‘theatrical’, paranormal, and vampire-hunting (using silver nails, we presume) interests.  Narrowing the search to “scholarly” sources, we found several peer reviewed papers that referenced a nail firing velocity of 1400 ft/sec and others that reported different velocities.  (Just to note, no articles were found using these search terms in PubMed or MedLine). All articles except one were medical journal case reports of nail gun injuries. The oldest and most frequently cited paper was from 1983, but this paper did not provide or reference an actual velocity measurement.[4]
The article we found that specifically cited the 1,400 ft/sec velocity value was written in 1997[5]. The earlier paper it referenced[6], however, did not report a specific nail gun velocity and instead alluded to the “driving force of the pin was the explosion of a .22-caliber (10mm) cartridge.”  While .22 caliber cartridges have variable velocities, some long-rifle .22-caliber cartridges are reported to include velocities in the 1400 ft/sec range.  The second article[7] describing specific velocities stated that “nail guns must be used with caution as they are capable of firing projectiles of up to 100 to 150 m/s and distances of up to 500 m.”  (Converted to ft/sec, these values are, respectively, 328 to 492 ft/sec). 
In 2001, a journal published a nail gun injury epidemiology article[8] based on an earlier report[9] that stated nail guns “can fire up to nine nails per second at velocities as high as 1,400 ft. per second.”  One year later an article was published[10] that included nail gun velocity data corresponding to measurements conducted by the CPSC [1] and Mr. Kelsey [2]. The data was collected by the authors themselves and reported they had “measured the velocity of experimentally fired nails with a ballistic chronograph … The velocity of the fired nails ranged from 97.7 to 121.1 ft/sec (mean: 105.5).”  Subsequent injury case reports in medical journals continued to reference varying ”nail gun” velocities, including 424 m/s (1391 ft/sec)[11] , 200 mph (293 ft/sec) [12]  and 293 ft/sec[13] .  Our “sleuthing” did find a 1975 reference in a medical journal that reported pneumatic nail gun muzzle velocities “being only 20 to 30 meters per second (66 – 98 ft/sec) 2 meters from the nailer muzzle.”[14]
How is it that so many different nail gun velocities were reported over so many years? The answer to this question appears straightforward.  Two types of fastening tools used in the construction industry to shoot fasteners into building materials have been called “nail guns”.  One tool uses an explosive charge and the other uses compressed air as energy sources to propel the fastener. The higher velocity tool is called a “powder actuated tool” (PAT)[15] and uses the explosive charge – often cordite – to propel the fastener.  The explosive charge is comparable to a .22-caliber ‘blank’. The resulting velocity, ranging from 315 ft/sec (96 m/s) to 1,295 ft/sec (395 m/s) [14] depends on the type of charge and whether the charge directly or indirectly propels the fastener.  Higher velocities produced in the PAT are used to drive fasteners into concrete or metal.
The far more common nail gun (or nailer) used to fasten lumber together uses compressed air to propel a piston to drive the nail into the lumber.[16]  These are pneumatic nail guns (PNGs).  PNGs are not engineered to penetrate concrete or metal materials and operate at much lower velocities than the PAT.
Many early “nail gun” injury case reports that appeared in medical journals described injuries occurring with both PATs and PNGs and incorrectly assumed that the velocities were comparable or made no effort to describe the differences.  An article published in 1986 that described both types of tools stated that the “driving force for the pin was the explosion of a .22-caliber (10 mm) cartridge.”[ 6] Eleven years later an article describing two PNG injuries referred to nail guns “used to fire nails into steel, masonry and wood” and went on to describe the tool’s “velocities as high as 1,400 feet per second.”  This article not only confused the purpose of the two types of tools, but indirectly attributed the higher velocity capability of the PAT to the PNG.  This article was later cited in the nailer injury epidemiology report in 2001. [8] One year later an injury case report [10] included PNG velocity measurements conducted by the authors that confirmed those reported by the CPSC [1] and Kelsey [2].
The PAT and PNG energy difference appears to matter most when an airborne fastener strikes the body at a distance or when a shot at a close distance strikes bone.  In each case the PAT propels the fastener with greater velocity, kinetic energy, and potential to cause a disabling or even fatal injury.  This is illustrated in the Discovery Channel television program “Mythbusters” that compared the penetration capacity of an airborne projectile shot from a pneumatic framing nail gun to that of a 9mm hand gun.   Though its intent is entertainment rather than scientific study, the “Mythbusters” segmentExternal Web Site Icon demonstrates quite clearly that pneumatic nail guns do not have the equivalent muzzle velocity of a hand gun or a PAT. 
Regardless of the lower velocity, pneumatic nail guns are dangerous tools.   Deaths and seriously disabling injuries have occurred when fasteners were shot from a pneumatic nail gun with immediate contact to the head, chest, or torso. It is in the pneumatic nail gun user’s best interest to handle these tools as if they were a firearm despite having a lower velocity.  We have provided a list of  resources below  that provide nail gun safety information.  There is no “myth” in stating that pneumatic nail guns can result in serious injury or even death.
Jim Albers, MPH, CIH; Brian Lowe, PhD, CPE; Stephen Hudock, PhD, CSP
NIOSH Organizational Science & Human Factors Branch, Division of Applied Research and Technology, Cincinnati, OH
Special thanks to Kathy Connick, Librarian, OSELS, who assisted our publication search.


Straight Talk About Nail Gun Safety 
Plática directa sobre seguridad con pistolas de clavos 
Nail Gun Safety: A Guide for Construction Contractors 
Seguridad con las pistolas de clavos: Guía para los contratistas del sector de la construcción
Nail Gun Safety: The Facts  External Web Site Icon(CPWR)

[1] Consumer Products Safety Commission (CPSC), [2002]. Evaluation of Pneumatic Nailers. Memo from Carolene Paul to Jacqueline Elder. May 23, 2002. See Adobe PDF fileExternal Web Site Icon. [2] Kelsey, H.B. (2000) Additional Information for Forensic Engineers Regarding Nail Guns.  Journal of the National Academy of Forensic Engineers, December, 2000.
[3] Harris T. How Nail Guns Work. Accessed June 27, 2013. Web Site Icon.
[4] Lyons FR. Industrial nail gun injuries. Med J Australia. 1983;2(10): 483–487.
[5] Hoffman DR, Jebson, PJL, Steyers, CM (1997) Nail Gun Injuries of the Hand. Am Fam Phys, Oct, 15, 1997 1643-1646.
[6] Edlich RF, Silloway KA, Rodeheaver GT, Morgan RF, Birk K, Thacker JG. Industrial nail gun injuries. Compr Ther. 1986;12:42–6.
[7] Beaver AC, Cheatem ML. Life threatening nail gun injuries. Am Surg 1999;65(12)192-5.
[8] Baggs J, Cohen M, Kalat J, Silverstein B. (2001) Pneumatic Nailer Injuries: A Report on Washinton State 1990-1998. Occupational Safety, Jan 2001 1:33-38.
[9] Baggs J, Kalat J, Cohen M, Silverstein B. (1999) Pneumatic Nailer (“Nail Gun”) Injuries in Washington State, 1990-1998
Technical Report Number:59-1-1999. Safety and Health Assessment and Research for Prevention (SHARP) Program
Washington State Department of Labor and Industries.
[10] Buchalter GM, Johnson LP, Reichman MV, et al. Penetrating trauma to the head and neck from a nail gun: A unique mechanism of injury. Ear Nose Throat J. 2002;81:779-783.
[11] Nizam I, Choong PFM. The nail gun: injuries to the knee and chest. Injury, Int J. Care Injured 34 (2003) 240-41.
[12] Horne BR, Corley FG. Review of 88 nail gun injuries to the extremities. Injury, Int J. Care Injured (2008) 39, 357-361.
[13] Rhee PC, Fox TJ, Kakar S. Nail gun injuries to the hand. J Hand Surg Am. 2013 Jun;38(6):1242-6. Epub 2013 Mar 28.
[14] Peterson CA, Dixon GL (1975) Pneumatic Injuries to the Bone, Letters to the Editor, Clinical Orthopaedics and related Research, No. 10, July-August, 1975, 334-6.
[15] Wikipedia (2013) Powder-actuated tool. Accessed June 28, 2013. Web Site Icon
[16] Nail gun. Wikipedia. Accessed June 28, 2013. Web Site Icon

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