Construction Peer-Reviewed Pneumatic Guns Revisiting Trigger Recommendations

By James Albers, Brian Lowe, Hester Lipscomb, Stephen Hudock, John Dement, Bradley Evanoff, Mark Fullen, Matt Gillen, Vicki Kaskutas, James Nolan, Dennis Patterson, James Platner, Lisa Pompeii and Ashley Schoenfisch

neumatic nail gun use is ubiqui- trigger systems that then define how the nail gun tous throughout the modern homebuilding fires in response to a trigger press: Pindustry. This has dramatically increased 1) The sequential actuation trigger (SAT) re- framing productivity beyond what could be achieved quires that each nail can only be discharged when with a hand . However, the dramatic in- the safety tip is first depressed and, while held de- crease in productivity introduced a new injury: pressed, the trigger is squeezed. You’re using a gun to do something faster, and 2) The contact actuation trigger (CAT) allows fast isn’t safe. . . . It might be making it easier, but the operator to first squeeze the trigger and, while all around, it’s shooting projectile at a high speed holding the trigger squeezed, repeatedly bump the to go through hard materials. It’s just dangerous safety tip on the workpiece to shoot multiple nails. to work with. (Union carpenter, St. Louis, MO) Of these two trigger mechanisms, the SAT pro- Before pneumatic nail guns vides a positive safety advantage (European Com- were available, nail puncture mittee for Standardization, 2009; Stanley Works, IN BRIEF injuries on a construction site 2002) in that it prevents the unintended firing of •Use of a pneumatic nail gun with typically occurred when a car- a nail that can otherwise occur when the trigger is a sequential actuation trigger (SAT) penter or other tradesperson depressed and the workpiece contact is bumped significantly diminishes the risk for stepped on a nail protruding (Photo 1, p. 32). acute traumatic injury compared to use from a piece of lumber. Car- Traumatic injuries can occur when an operator of a nail gun equipped with a contact penters did not accidentally using either type of actuation device intention- actuation trigger (CAT). drive nails into their own bodies ally discharges a nail that subsequently penetrates •A theoretically based increased or that of a coworker with re- through the or misses it altogether. However, risk of work-related musculoskeletal peated strikes from a hammer. an SAT-equipped nail gun is much less likely to be disorders from use of an SAT nail gun, However, such injuries became discharged unintentionally, as the trigger must be relative to CAT, appears unlikely and more common when pneumat- activated while the safety tip is depressed against remains unproven. ic nail guns were introduced to the workpiece (NIOSH/OSHA, 2011). •Based on current knowledge, use of drive nails at a high speed to go Unintentional nail discharge using a CAT- CAT nail guns cannot be justified as through hard materials. equipped device typically occurs following nail gun a safe alternative to SAT nail guns. Pneumatic nail guns have a recoil (resulting in a double fire—a second, unin- The authors, who are ergonomists and safety device (workpiece con- tended shot) or when the operator has his/her finger occupational safety researchers, rec- tact, nose, yoke, tip) at the end on the trigger and the nail gun nose inadvertently ommend the use of the SAT for all nail of the gun muzzle that must be contacts an object (Lipscomb, Dement, Nolan, et gun tasks in the construction industry. depressed before the fastener al., 2003). Although operators are advised to not can be discharged. Generally, hold the trigger in the depressed position when these devices have two types of not intending to shoot a nail, a nail gun’s physical characteristics, including weight (8 lb to 9 lb), bal- ance, trigger location and hand-grip design, make it easier to hold the gun with a full power grip that Author Affiliations includes the index finger (Photos 2 and 3, p. 32-33). •NIOSH: James Albers (retired), Brian Lowe, Stephen Hudock and Matt Gillen (retired) •Duke University: Hester Lipscomb, John Dement and Ashley Schoenfisch Nail Gun Injury Studies •Washington University: Bradley Evanoff and Vicki Kaskutas Portable pneumatic nail guns have been used to •West Virginia University: Mark Fullen frame new wooden structures since the mid-1960s •Carpenters District Council of Greater St. Louis and Vicinity: James Nolan and and gradually replaced the framing hammer as the Dennis Patterson tool of choice. As pneumatic nail gun use increased •Center for Construction Research and Training: James Platner •University of Texas Health Science Center: Lisa Pompeii in the 1980s and 1990s, so did the number of medi- cal case reports of pneumatic nail gun fatalities and

30 ProfessionalSafety MARCH 2015 www.asse.org traumatic injuries to the head, eyes, chest, and the Lipscomb, et al. (2003), investigated all acute lower and upper extremities. work-related injuries (n = 783) among a St. Louis, Washington State Department of Labor and In- MO, carpenters’ union apprentice cohort working dustries published the first nail gun injury epide- in the residential building industry (1999-2001). miology report in 1999 (Baggs, Cohen, Kalat, et al., Nearly 14% (80) of the injuries involved nail gun 1999) and a version of it was later published in Pro- use. The rate for apprentice carpenters was higher fessional Safety (Baggs, Cohen, Kalat, et al., 2001). (3.7/100 FTEs) than that of journey-status carpen- The study reported an analysis of workers’ compen- ters (1.2/100 FTEs). A majority of injuries occurred sation claims for nail gun injuries that occurred from when the CAT mechanism was used and the au- 1990 to 1998 in Washington State. The injury inci- thors concluded that 65% of the injuries could have dent rate for building construction workers (SIC 15, been prevented had the nail guns been equipped Building Construction) was 78 incidents per 10,000 with an SAT mechanism. full-time equivalent (FTE) workers/year, while the Lipscomb and Jackson (2007) analyzed reports of incident rate for wood framing tasks was 206 per nail gun injuries treated in U.S. hospital emergency 10,000 FTE. departments from 2001 to 2005. The range in annual Dement, Lipscomb, Li, et al. (2003), analyzed occupational related injuries was 19,300 to 28,600, Ohio Bureau of Workers’ Compensation claims with an annual average of 22,200. Most injuries (1994-97) for all Ohio carpenters and residential were to the upper extremities (66%) and lower ex- construction workers employed (1996-99) by North tremities (24%); bone fractures were involved in 4% Carolina Home Builders Association members. Nail of the injuries. The data did not include information gun injury rates for the North Carolina and Ohio describing nail gun actuation systems being used cohorts were 91 cases/10,000 FTE and 132/10,000 when the traumatic injuries occurred. FTE, respectively. A subset of claims was analyzed Clearly, using pneumatic nail guns presents the (n = 185) that included written narrative descriptions potential for serious injury or death. An unpub- of the injury incident and the authors concluded that lished review of nine nail-gun-related fatality in- at least 69% of the incidents may have been the re- vestigations in the OSHA Integrated Management sult of an unintentional nail gun discharge or misfire. Information System revealed three cases that were www.asse.org MARCH 2015 ProfessionalSafety 31 Photo 1: The full SAT nail gun is safer because it requires that the two con- trols be actuated in a specific sequence. First, the safety tip is pressed against the lumber (left panel), then the trig- ger is depressed to fire the nail (middle panel). When the nail gun fires, recoil of the tool away clearly attributable to the CAT trigger (that is, pre- SAT systems. For example, in 2001, the New Zea- from the workpiece ventable with SAT) and five cases that lacked ad- land Department of Labor published “Guidelines (right panel) can equate information to clearly determine the role of for the Safe Use of Portable Mechanically Powered result in a second, trigger type in causation. Only one fatality case was Nailers and Staplers.” These guidelines acknowl- unintended, contact deemed to have been clearly unpreventable with edge risk of overuse syndrome with SAT, but only of the safety tip. SAT. It is also known that the SAT system provides in high-volume production when “thousands of With the SAT, a a positive safety advantage over the CAT system. trigger pulls every day” are required. The New nail will not fire Despite this, the CAT system is more likely to be Zealand guidelines only allow for CAT use under on the second used than the SAT system. safely managed high-volume pallet and wood crate contact because One anecdotal argument against using the SAT assembly operations (not construction work) when the trigger must system is the potential for developing trigger finger a number of nail gun management, operator train- first be released (stenosing tenosynovitis) as a result of the need to ing and workstation design requirements are met. and then actu- squeeze the trigger for each nail discharged. Baggs, The authors suggest that theoretical concerns ated after the safety et al. (2001, p. 37), provide an opinion that nail gun about the development of specific stenosing teno- tip. Conversely, a operators use the SAT system. However, the ear- synovitis symptoms from use of SAT-equipped de- CAT-equipped nail lier SHARP report (Baggs, et al., 1999) included the vices have not been confirmed by either surveillance gun fires with the following: or biomechanical evidence. A recent NIOSH study controls actuated As employees gain experience with the tool, the conducted to assess finger displacement and pre- in either sequence “bump” (CAT) trigger system can be implement- dicted finger tendon travel did not result in cumula- and the trigger need ed to reduce the potential risk of musculoskel- tive tendon travel at the levels previously associated not be released etal disorders (e.g., trigger finger). Manufacturers with hand/wrist musculoskeletal disorders (Lowe, between successive should work with users and safety profession- Albers, Hudock, et al., 2013). nails fired. als to better balance speed and productivity of A second NIOSH study (Albers, Hudock & Lowe, using the “bump” mode with accuracy and po- 2013) queried residential building framing sub- tential for fewer acute trauma injuries using the contractors and carpenter working in nine sequential mode. In all cases, the possibility of focus groups conducted in five states. Some focus trigger finger must be considered. group participants described having developed or The technical report and subsequent article knowing someone who developed carpal tunnel (Baggs, et al., 1999; 2001) recommend that the SAT syndrome related to nail gun use, irrespective of should be used, postulating that the SAT device the trigger mechanism they used. No participant, likely poses less traumatic injury risk to the user. however, described the same for trigger finger with As such, less experienced nail gun users were en- either actuation system. couraged to use the SAT to reduce the likelihood of injury. Transition to a CAT-equipped nail gun was opined to provide speed and productivity advan- tages over the SAT and diminish risk for musculo- Photos 2 and 3: skeletal disorders, implying a possible differential It is natural and risk for work-related musculoskeletal disorders more efficient between SAT and CAT nail guns. These opinions to grip a tool were not necessarily intended as policy guidelines. handle with a In the years since these documents were published, full power grip, no evidence has emerged in the medical case re- which includes port, or the ergonomic or injury epidemiology lit- use of the index erature to indicate that use of the safer single-shot finger in the grip. SAT trigger mechanism differentially increases a With most nail worker’s risk of developing a work-related muscu- guns, the index loskeletal disorder. finger must actu- Other guidance at that time also suggested that ate the trigger to risk factors for cumulative trauma disorders/repeti- contribute to the tive strain injury be considered in the adoption of grip of the tool.

32 ProfessionalSafety MARCH 2015 www.asse.org None of these observations specifically refutes movements and awkward postures associated with a potential association between SAT use and fin- construction tasks and nail gun use irrespective of ger tendon cumulative trauma. Collectively, how- the triggering mechanisms used. ever, they cast serious doubt on the existence of a However, at present, no evidence shows that problem—for which no documentation exists—at- the SAT differentially increases risk of developing tributable to a specific trigger system. When con- trigger finger or any other work-related musculo- trasted with the overwhelming evidence in support skeletal disorder. In contrast, overwhelming epi- of traumatic injury risk reduction with the SAT, it demiologic evidence indicates that the CAT trigger seems imprudent to justify any recommendation mechanism increases the risk of unintentional nail other than the use of SAT in the context of con- discharge and associated injuries, and that the struction safety and health. SAT trigger mechanism provides a positive safety Unfortunately, the awareness of overuse syn- advantage. Given the current state of evidence re- drome potential can be easily cited out of context, garding traumatic and cumulative trauma injury creating the impression that overuse syndrome is risks in construction, “the full sequential trigger is differentially associated with SAT use in construc- always the safest trigger mechanism for the job” tion work with nail guns. Misappropriated empha- (NIOSH/OSHA, 2011, p. 6). PS sis on the theoretically based causation of repetitive motion injury (e.g., trigger finger) may distract from References the evidence-based acute traumatic injury risk. This can be seen clearly in nail-gun injury litiga- Albers, J., Hudock, S.D. & Lowe, B.D. (2013). tion defense and in recommendations from OSH Residential building stakeholders’ attitudes and beliefs regarding nail-gun injury risks and prevention. New agencies. For example, in Martin Oliver v. Hitachi Solutions: A Journal of Environmental and Occupational Koki USA Ltd. (2012), the defense drew specific at- Health Policy, 23(4), 577-605. tention to the SHARP (Baggs, et al., 1999) and New Baggs, J., Cohen, M., Kalat, J., et al. (1999). Pneu- Zealand (2001) documents to justify use of CAT matic nailer (“nail gun”) injuries in Washington State, based on a theoretical reduction in repetitive mo- 1990-1998 (SHARP Technical Report No. 59-1-1999). tion injury risk. In a 2009 Hazard Alert on nail guns, Retrieved from www.lni.wa.gov/safety/research/files/ Oregon OSHA described nail gun safety hazards. nail_gun.pdf However, one recommendation stated, “Use the Baggs, J., Cohen, M., Kalat, J., et al. (2001). Pneumatic bump action trigger for . . . rapid nailing on flat, sta- nailer injuries: A report on Washington State 1990-1998. tionary surfaces such as decking, sheathing and sid- Professional Safety, 46(1), 33-38. Dement, J.M., Lipscomb, H., Li, L., et al. (2003). Nail ing. This mode is very fast and can reduce the risk gun injuries among construction workers. Applied Oc- of musculoskeletal disorders such as trigger finger.” cupational and Environmental Hygiene, 18(5), 374-383. In the authors’ view, an unintended conse- European Committee for Standardization. (2009). quence of the recommendations published in 1999 Handheld nonelectric power —Safety require- and 2001 has been the creation of the appearance ments—Part 13: Fastener driving tools (EN 792-13:2000, of competing risks with nail gun trigger systems. A1:2008). Brussels, Belgium: Author. This may undermine policy efforts to reduce the Lipscomb, H.J., Dement, J.M., Nolan, J., et al. (2003). high prevalence of traumatic injury attributable to Nail gun injuries in residential carpentry: Lessons from CAT-equipped devices. active injury surveillance. Injury Prevention, 9(1), 20-24. Lipscomb, H. & Jackson, L. (2007). Nail-gun injuries treated in emergency departments: U.S., 2001-2005. Conclusion Morbidity and Mortality Weekly Report, 56(14), 329-332. Work-related musculoskeletal disorders among Lipscomb, H.J., Nolan, J., Patterson, D., et al. (2008). carpenters and other construction workers are a How much time is safety worth? A comparison of trig- genuine concern. Additional research is needed ger configurations on pneumatic nail guns in residential on risk factors such as forceful exertions, repetitive framing. Public Health Reports, 123(4), 481-486. Lowe, B., Albers, J., Hudock, S., et al. (2013). Finger tendon travel associated with sequential trigger nail gun use. IIE Transactions on Occupational Ergonomics and Hu- man Factors, 1, 109-118. Martin Oliver vs. Hitachi Koki USA Ltd. (2012). Reporter’s transcript of trial proceeding, April 11, 2012. Disclaimer Superior Court of the State of California for the County of San Bernardino, CA. The find- NIOSH/OSHA. (2011). Nail gun safety: A guide ings and for construction contractors (NIOSH Publicasation conclusions No. 2011-202). Retrieved from www.cdc.gov/niosh/ in this article docs/2011-202 are those of New Zealand Department of Labor. (2001). Guidelines the authors for the safe use of portable mechanically powered nailers and do not and staplers. Retrieved from http://bit.ly/1CeM1Jb necessar- Oregon OSHA. (2009). Hazard alert: Pneumatic nail ily represent and gun safety (OR-OSHA 2993-21). Retrieved from www.cbs.state.or.us/osha/pdf/hazards/2993-21.pdf the views of Stanley Works. (2002). Industrial tools and fasteners NIOSH. (Catalog AD4020). East Greenwich, RI: Stanley Fasten- ing Systems LP. www.asse.org MARCH 2015 ProfessionalSafety 33