Investigation Guidelines

Investigation Guideline
Product: Chain Saws
Appendix # : 2
Date amended: May 4, 2005
I. Introduction
A. Background Information
The Directorate for Epidemiology estimated that about 25,560 injuries were treated in
U.S. hospital emergency rooms associated with chain saws for the calendar year 2002. The
number of deaths involving chain saws reported to the Commission varies from 12 to 23
deaths per year between the calendar years 1995 and 2001.
The major hazard pattern identified with chain saw was kickback – which was
estimated at 20 percent of injuries and almost half of the deaths. Rotational kickback is
defined as a sudden upward or rearward movement of the chain saw. It most often occurs
when the saw chain moving around the nose of the guide bar accidentally touches another
object such as log, branch, or twig. Contact like this can throw the chain saw violently back
toward the operator. Kickback can also occur when the moving chain on the top of the guide
bar is pinched in the cut or binds in the wood; this is known as pinch kickback. Although the
major single hazard pattern identified with chain saw was kickback, about three fourths of the
injuries are non-kickback injuries including numerous scenarios resulting in the saw striking
the victim. Identified non-kickback hazard patterns include: chain saw skating or bouncing,
loss of saw control, follow-through after cut, loss balance (operator), unaware of bystander
location, and falling tree or tree branch. In addition, miscellaneous injuries occur when the
victim inadvertently contacts the moving chain or coasting chain during position changes, or
even when the victim contacts the non-operating chain during repairs or other handling. More
investigations are needed to monitor these hazard patterns in order to reduce the frequency of
injuries through additional standards or information campaigns.
From 1979 to 1985, the primary focus of the Commission was on rotational kickback
hazards. The CPSC staff participated with the chain saw industry in developing amendments
to the American National Standards Institute (ANSI) voluntary standard for gasoline powered
chain saws, B175.1 –1985, to reduce the likelihood that rotational kickback would result in
serious injury and death. Since 1985, the focus has been on non-kickback hazards,
particularly those involving skating/bouncing and one-handed operations. In 1986, voluntary
standard for electric chain saws was published. In the same year, the commission confirmed
virtually 100 percent conformance of new saws to kickback standard.1
1

Letter from CPSC Chairman Terrence Scanlon to Mr. Donald Purcell, President, Portable Power
Equipment Manufacturers Association, November 23, 1987.

The current standard for gasoline chain saws is ANSI B175.1-2000. It full title is
“American National Standard for Power Tools – Gasoline – Powered Chain Saws – Safety
Requirements.” It was last revised on October 27, 2000. In June 2002 this standard was
changed from the ANSI committee process to the ANSI canvass process. CPSC is on the
canvas list for this standard. As a result, CPSC will be asked to provide comments on any
potential changes to the standard as a part of the ANSI approval process. The next ANSI
required revision to the standard is to be in 2005 2.
The current standard for electric chain saws is UL 1662-1998. It was last revised on
April 8, 1998. CPSC has not participated in this standard. The standard has “Kickback”
provision that was adopted from ANSI B175.1. The next required revision to the standard is
to be in 2003 3.

B. Product Descriptions
Gasoline and electric chain saws can be used for many purposes – cutting firewood,
clearing land, or trimming trees. Chain saws are powerful and efficient tools, but they can be
very dangerous and, therefore, must be used with great care. Most chain saws are comprised
of the following parts:
1. Saw Chain
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Describe any missing or broken parts.
Determine looseness or tightness of chain. Note if there is visible sagging of chain at
bottom of guide bar.
Determine if chain is self-sharpening type.
Determine if chain is sharp or dull. Try to discover amount of cutting time since
chain last sharpened.
Determine the age of chain. Is it original or replacement? Who installed chain on
saw? Try to obtain estimate of useage hours.
Determine whether it is a low kickback chain that is capable of reducing chain saw
kick back.
Describe any other chain problems known to owner or operator.

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2.Guide Bar
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Was it a reduced-kickback guide bar (which has been demonstrated to reduce
kickback significantly)?
Guide bar brand name.
Guide bar shape - symmetrical, asymmetrical, or bow.
Guide bar tip (difference is presence of teeth on nose of guide bar): solid (without
teeth) or sprocket (with teeth).

Murphy, John R., ESME, Directorate for Engineering Sciences, CPSC – September 30, 2003.
ibid

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Guide bar length (from the tip of the nose to front handle), in inches.

3. Hand Guard
A hand guard, when present, will be found between the front handle of the saw
and the guide bar and is intended to prevent the hand from contacting the chain. They
often may be attached to, or part of, the chain brake mechanism. Hand guards may be
solid or have open areas and may be rigid or somewhat flexible. One common hand
guard is the non-wrap around which extends only over the area in front of the upper
portion of the front handle (Figure 1). Another is the wrap around which parallels both
the upper and left side of the front handles (Figures 2-3 in different angles). Determine
the following with respect to the hand guard:
• Did the chain saw have a hand guard when it was purchased or acquired? Was it on
the saw at the time of accident? If not, determined why not.
• Described hand guard on the saw at the time of accident if it was physically attached
to the saw.
• Described hand guard condition at time of incident (i.e., broken, bent, or in good
condition).
• Determine if hand guard bent or deflected during the incident?
• Determine and describe any permanent damage that may have occurred to hand guard
during incident and how it might have happened.

Figure 1

4. Chain Brake (A device used to stop the saw chain, Figure 1). Determine the following:
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Was chain brake attached to the saw at the time of purchased?
Was it operating at the time of the incident?
Was it adjusted/serviced just before the incident? Give time since last adjustment.
Were there problems associated with chain brake?

5. Nose Tip Guard/Bar-Tip Guard
A shield that prevents contact with the chain at the tip of guide bar and which may
be removable and replaceable (Figure 1). Determine the following:
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Was it factory attached to the saw when purchased or obtained?
Was it attached at the time of incident?

Figure 2

Figure 3

C. Specific Items of Interest
Incidents involving chain saws require information on product, brand, model,
cubic inch displacement (CID), amperage (Amps), as well as details about the chain,
guide bar, and safety devices such as hand guard, nose tip guard, and chain brake (see
illustrations). Include all gasoline and electrical powered chain saws.

C. Headquarters Contacts
Natalie Marcy, EPHA – (301) 504-7329
John Murphy, ESME –(301) 504-7541

II. Instructions for Collecting Specific Information
A. Synopsis
Please provide a summary of the sequence of events that occurred prior to and during
the incident that includes the following important information:
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Position of the saw.
Position of the operator.
Position of the victim (if not operator).
Position of object being cut.

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Whether the saw was inside the cut or just being directed to the wood (or kickback
object).
Direction of injuries (vertical or horizontal).
Object causing kickback.

B. Description of Incident Environment
Describe the location and environment of the incident, working areas, and object being
cut. Also describe operator’s intended actions, e.g., limbing, bucking, felling, or clearing prior
to the incident and the following:

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Any adverse weather conditions, temperature, wind speed, and direction, rain,
snow, etc.
Lighting conditions at the time of the incident.
Where operator/victim was standing (condition, shape, and material), e.g., on pile
of logs (one foot diameter or stacked three feet high).
Ground surface conditions, e.g., wet/dry, or slippery.

C. Description of Interaction between Injured Person(s) and Product
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Stipulate the type of material being cut, length/diameter, hard wood, softwood,
condition of wood – frozen, wet, knotty, green, or rotted.
Specify whether operator held saw with one or both hands.
Specify position of hands and feet.
Describe grip on front handle, firm/relaxed, elbow locked/bent.
If one-handed operation, describe how saw was held and activity of hand not
holding saw.
Indicate whether trigger was released at the time of accident.
Indicate whether chain was moving (running, coasting, stopped) at the time of the
incident (note chain brake activation).
Describe orientation of saw to wood being cut: cutting edge (upper or lower
blade), angle of entry, position of the operator (or victim) relative to saw and
wood.
Indicate if guide bar was parallel, perpendicular, or some other angle to the
ground.
Describe object that causing kickback; whether object being cut or other (specify).
Describe where object contacted chain or guide bar: tip (mid, upper, lower), bar
top, bar bottom, other (specify).

D. Description of Victim Contact
State whether the victim was the operator, helper, or bystander. Including victim’s
age, sex, and severity of injury. Obtain the following information:
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Exact body part injured (i.e., palm, or back of hand) and length of laceration
(number of sutures).
Days of hospitalization, work loss, temporary or permanent disability
Handedness of operator.
Experience with chain saw and length of experience.
Operator’s condition at the time of injury e.g., tired or distracted.
Operator’s age and sex, if not victim.
Duration of saw use that day.
How long the operator had been using chain saw with the chain turning (prior to
injury).
Any medication victim took and whether victim had any competence reducing
physical or medical handicaps.
Alcohol consumption.
A complete description of clothing and safety equipment in use (e.g., sure-grip
gloves, safety shoes, safety goggles, hard hat, hearing protectors).

III.Photographs/ Diagrams of Incident Scene
Accident involving chain saw kickback require at least two profile photographs from
which we intend to determine the angle or arc the saw rotated or traveled during the incident.
(1) WITHOUT POWER TO THE SAW, have the operator duplicate the position of the
saw and his body at the moment before the incident (also position victim if not operator).
(2) WITHOUT POWER TO THE SAW, have the operator stand in the position as he was
struck. The saw should be in the striking position. In theory only the saw, operator’s
hands, arms, and torso have moved from the first to the second pictures. The feet
probably have not moved (also position victim if not operator).
(3) WITHOUT POWER TO THE SAW, take one picture (front view, full figure) which
will show the position of the right and left hands on the saw and position of the saw
relative to the body as the operator was standing at the time of the incident.
(4) WITHOUT POWER TO THE SAW, take one picture of the operator’s hands on saw
handles as they were at the time of the incident.
(5) WITHOUT POWER TO THE SAW, take (close-up) pictures of chain saw, chain,
guide bar (brand, shape, length, and guide bar tip), and hand guard/chain brake.

IV. Obtaining samples and documents related to the investigation
Obtain operator instruction manual, if available. Obtain copy of labeling, or transcribe
label. In case of fatality, obtain medical examiner reports and police/sheriff or fire marshal
reports if possible.

(DATA RECORD SHEET ATTACHED)

DATA RECORD SHEET
Investigation Guideline
PRODUCT:_Chain Saws_______________
TASK NUMBER __________________________ INCIDENT DATE ___________________________

1. Is the chain saw that was used at the time of the incident gas or electric?

2. Had the chain saw been changed or modified in any way? How was the saw changed
or modified?

3.At the time of the incident was the operator using a low kickback chain (stops before
the saw reaches the 45 0 angle)?

4. Has the operator/owner ever replaced the chain? How often does he/she replace the
chain?

5. What is the brand name of the chain that the operator used with the saw at the time of
the incident?

6. Did the operator/owner of the saw receive safety instructions with the replacement
chain?

7. Does the chain saw have a self-sharpening feature?

8. In the last year, how many times, if ever, has the operator/owner sharpened or filed
the chain him/herself?

9. What kind of guide bar was on the chain saw at the time of the incident, was it
symmetrical, non-symmetrical, or bow?

10. What was the length, in inches of the guide bar? (length is measured from the
housing of the engine to the tip of the bar).

11. Has the operator/owner ever replaced the guide bar? How many times in the last
year?

12. Did the saw that was used at the time of the incident have a chain brake as a safety
feature?

13. Did the chain brake come with the saw or was it purchased separately?

14. Does the operator use the chain brake to stop the chain in addition to it’s being a
safety feature?

15. At the time of the incident, had the chain brake been activated?

16. Was the chain brake operating properly?

17. Did the saw used at the time of the incident have a nose-tip guard (“noz guard”) as a
safety feature?

18. Was the nose-tip guard attached to the bar of the saw when purchased, borrowed, or
rented?

19. Does the operator/owner always leave the tip on or take it off?

20.When does the operator/owner remove the nose tip guard?

21. About what percent of the time does the operator/owner use the nose-tip guard?

22. Did the saw have a front hand guard as a safety feature when purchased?

23. What type of front hand guard is attached to the saw at the time of the incident?

24. Does the saw have on it a label with letters “UL” and the statement that the chain saw
meets the ANSI B 175.1-2000, the American National Standard for powered
chainsaws?

25. In the operator’s opinion, what caused the incident?

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