2.09k likes | 4.2k Views
Working at height Full body harness, Safety lanyards, Lifelines. Corporate Health & Safety 2011. Summary. Introduction Main causes of accidents Individual protection Questions. Introduction. February 2010 Fatality Work: removal snow works on the roof of the Rail Finishing Bay
E N D
Working at heightFull body harness, Safety lanyards, Lifelines Corporate Health & Safety 2011
Summary • Introduction • Main causes of accidents • Individual protection • Questions
Introduction February 2010 Fatality Work: removal snow works on the roof of the Rail Finishing Bay The worker falls from the roof 20 m high
Introduction May 2010 Fatality Work: install an additional drain pump on the concrete roof (slab) of the pumping station The worker falls from the roof 6.2 m high
Introduction September 2010 Fatality Work: replacement of asbestos cement plates by metal plates The worker falls from the roof 17 m high
Main causes of accidents Not using the lanyard Not wearing full body harness Not using a controlled anchorage point Not adjusting the harness Not checking the fall clearance Not working with rescue plan and safety watch Not checking the arrest force Not controlling of the harness' state
What Happens in a Fall with a 1.8 m (6 ft) lanyard? Time Physical Response Free-Fall Distance Velocity 0.1 sec Unaware 5.1 cm (2 in) 1.0 m/s (3.3 ft/s) 0.2 sec Aware 20.3 cm (8 in) 2.13 m/s (7 ft/s) 0.5 sec Start to Move 1.22 m (4 ft) 4.88 m/s (16 ft/s) 0.61 sec Slight Movement 1.83 m (6 ft) 5.97 m/s (19.6 ft/s) 0.7 sec Impact 2.41 m (7.9 ft) 7.01 m/s (23 ft/s) 0.9 sec Rebound 3.96 m (13 ft) 8.84 m/s (29 ft/s) 1.0 sec Suspend 4.9 m (16 ft) 9.75 m/s (32 ft/s)
History of falls • In industry, falls from heights : major cause of fatal or disabling accidents last 20 years. • In 95% of falls there is no second chance. • 80% of fall accidents occur at distances less than 6 meters. • 80% of people who fall at a height equal to or greater than 3.5 meters dies. • Many accidents happen because a person is only working at height for a few moments. ArcelorMittal – Only steel Industry (Own Employees and Contractors)
ArcelorMittal Regulations Group Companies will, as a minimum, follow the prevailing local regulations for elevated work where there is a risk of falling. Where this ArcelorMittal standard is more demanding, then it will apply. In any case, fall prevention or protection shall be used for elevated work above 1.8 meters (6 feet). However, for any task where the risk assessment highlights a danger of falling, proper actions have to be taken, even if the distance, one can fall, is less than 1,8 m. • A person will be subjected to Fall Protection if s/he is secured with an approved full body harness, shock absorbing lanyard (where the potential to fall is greater than 4 meters (13.3 feet) or short restraining lanyards (where the potential to fall is less than 4 meters), self-locking snap hooks (or carabineer type rings) and secure anchorage points (or life-line). • Safety belts are not adequate fall protection mechanisms and do not comply with ArcelorMittal standard.
Fall Hazard Analysis Before finding a solution – the Hazard must be evaluated. Use Hazard or Risk Prediction -- What are the conditions and behaviors to consider? How will we get to the work area? What are the hazards below the work area (hazard in case of falling, obstacles or electrical rails below working area, …)? How high is the work area? Are there holes or openings below or around the work area? Is the surface on which people are to walk is stableand strongenough ? Are there slip or trip hazards around the work area? How difficult is it to rescue someone if the fall (wearing or not an harness)?
Hazard or Risk Prediction Example: How will we get to the work area? What are the hazards below the work area? How high is the work area? Are there holes or openings below or around the work area? Is the surface on which people are to walk is stableand strongenough ? Are there slip or trip hazards around the work area? How difficult is it to rescue someone if the fall?
Solution Choices Use the Hierarchy of Control Elimination Substitution Engineering Administrative Collective Protective Equipment Personal Protective Equipment Each choice has its place and time Before making the choice(s), Evaluate the Problem
Table of content • Full Body Safety Harness • Fall Protection Categories • Fall Protection Systems • Lanyards • Calculating Fall Clearance Distance and force • Life lines • Nets • Anchorage points • Harness (and Body Belt) Inspection • Lanyard Inspection • Self-Retracting Lifeline Inspection • Harness and Lanyard Cleaning • Utilization of a translation wagon in horizontal lifelines • Wearing a Full-Body Harness 14.1) Donning a Harness 14.2) Wearing a Full-Body Harness 14.3) Proper Harness Fit 14.4) Donning a Pullover Front D-Ring Harness 14.5) Buckle Connection Instructions 14.6) Buckle Connection Instructions 14.7) Buckle Connection Instructions 14.8) Proper Use of D-Rings 15) Rescue Plan
1) Full Body Safety Harness FULL BODY HARNESS MODELS are available in many models with various options depending on their intended use: B:CONFINED ENTRY / RETRIEVAL HARNESS:Has one attachment point located on each shoulder strap to facilitate upright retrieval from confined spaces or frontal attachment. C:LADDER CLIMBING HARNESS: Has frontal attachment point for connection to permanent ladder safety systems. A:DESCENT CONTROL HARNESS:Has frontal attachment points for use with descent control devices. D:WORK POSITIONING HARNESS:Positioning D- rings are located on the hips for use with pole straps or work positioning lanyards to allow hands-free operation. (These may include integral waist belts attached to the harness.) E:MULTI-PURPOSE HARNESS:This may include extra attachment points to allow work in a variety of situations. The dorsal D-ring must always be used for fall arrest. The belt and pad provide additional back support, positioning rings and tool carrying options.
2) Fall Protection Categories All fall protection products fit into four functional categories. 1. Fall Arrest; 2. Positioning; 3. Suspension; 4. Retrieval.1) Fall ArrestA fall arrest system is required if any risk exists that a worker may fall from an elevated position, as a general rule, the fall arrest system have to be used anytime a working height of six feet or more is reached without collective protection. Working height is the distance from the walking/working surface to a floor or lower level. A fall arrest system will only come into service should a fall occur. A full-body harness with a shock-absorbing lanyard or a retractable lifeline is the only product recommended. A full-body harness distributes the forces throughout the body, and the shock-absorbing lanyard decreases the total fall arresting forces (dissipating energy during fall or shock).2) PositioningThis system holds the worker in place while keeping his/her hands free to work. Whenever the worker leans back, the system is activated. However, the personal positioning system is not specifically designed for fall arrest purposes.3) SuspensionThis equipment lowers and supports the worker while allowing a hands-free work environment, and is widely used in window washing and painting industries. This suspension system components are not designed to arrest a free fall, a backup fall arrest system should be used in conjunction with the suspension system.4) RetrievalPreplanning for retrieval in the event of a fall has to be taken into consideration when developing a proactive fall management program.
3) Fall Protection Systems Listed below are different types of fall safety equipment and their recommended usage.
Twin Forked Elasticated Lanyard Nylon shock absorbing lanyard Polyester restraining lanyard Webbing fall arrest block Double Nylon shock absorbing lanyard 4) Lanyards: Shock absorbing lanyard and short restraining lanyards
Energy Absorbing Lanyard Energy absorber shock pack Double locking snap hooks, or locking carabiner Use minimum length for the work to be done – no longer than 1.8 m (6 feet) 4) Lanyards: Shock absorbing lanyard and short restraining lanyards
Illustration: 6ft.(1.8m) Shock-Absorbing Lanyard with D-Bolt Anchorage Connector Length of Anchorage Connector Length of Lanyard Deceleration / Free Fall Distance (.3m) Harness Stretch Fall Arrest Distance Illustration: Self-Retracting Lifeline with D-Bolt Anchorage Connector Height of Worker To Worker’s Back D-Ring Safety Factor Bottom of Retractable Maximum Free Fall Distance Maximum Arrest Distance (per ANSI) Height of Worker Maximum Deceleration Distance (.3m) Harness Stretch To Worker’s Back D-Ring Safety Factor 5) Calculating Fall Clearance Distance • It is important to understand how to calculate potential fall clearance to avoid contact with a lower level. • The following diagrams demonstrate sample calculations using a shock-absorbing lanyard and self retracting lifeline. • When actually calculating fall clearance distance, the authorized person/user must consider all variables, including but not limited to: • the height of the worker • the length of the lanyard • the maximum arrest distance of the self-retracting lifeline, • the position of the person (standing or crouched) • the anchorage connector used, • and then make necessary adjustments to the calculations. Always refer to the instruction manual of the connecting device being used for more specific information and warnings regarding calculating fall clearance distance
5) Calculating Fall Clearance Distance Don’t forget to take into account the pendulum zone (in red on the drawing) SWING FALLS: Swing falls occur when the anchorage point is not directly above the point where a fall occurs. The force of striking an object in a swing fall may cause serious injury or death. Minimize swing falls by working as close to the anchorage point as possible. Do not permit a swing fall if injury could occur. Swing falls will significantly increase the clearance required when a self retracting lifeline or other variable length connecting subsystem is used. ENVIRONMENTAL HAZARDS: Use of this equipment in areas with environmental hazards may require additional precautions to prevent injury to the user or damage to the equipment. Hazards may include, but are not limited to: heat, chemicals, corrosive environments, high voltage power lines, gases, moving machinery, and sharp edges.
Maximum Arresting Force Force on the body caused by stopping a fall Maximum is 8 kN (1,800 lbf) by USA law Maximum is 6 kN (1,350 lbf) by European law Minimum force causing body damage = 12kN (2,700 lbf) All PPE is designed for a maximum free fall distance of 1.8M (6 ft) and a maximum arresting force of 8 kN (1,800 lbf, USA limit) or 6 kN (European limit). YOUR GOAL: Minimize the Free Fall Distance and minimize the Maximum Arresting Force 5) Calculating Force
6) Life-lines: Ladder Climbing Device Ladder Climbing Device -- • Used with Fixed Ladders • Used with a full body harness • Minimal length lanyard connected in front
Vertical Lifelines Rope Grabs 6) Life-lines: Vertical Lifeline Requires a Qualified Person for engineering or anchorage certification
Horizontal Lifelines Requires a Qualified Person for engineering or anchorage certification 6) Life-lines: Horizontal Lifeline All work and visits on a roof (including cleaning) require fall protection. If a lifeline is required, the lifeline must be engineered, tested and installed by competent persons.
Nets Frequently used with both horizontal and vertical lifelines Permit to secure the area below the working area (debris or tools containment, …) For all kind of construction applications and repairs (Roof work, maintenance, …) AM Standard: Collective protection, such as nets underneath the roof, are to be used at all times (unless a proper risk analysis clearly leads to the conclusion that would not be needed for the task at hand). 7) Nets
Characteristics Meets the strength requirement Identified Available for routine work Easy to use Who specifies the anchorage point? Must be a qualified person Reviewed and certified by a qualified engineer Can use both temporary and permanent anchorage points Ensure that the anchorage point is high enough (i.e. above the person to reduce fall height) for the PPE selected 8) Anchorage points
8) Anchorage points What if I don’t have an identified anchorage point? • Use a horizontal building structural beam (> 30 cm (12 inches) deep and distance between supports < 7.5 m (25 ft)) What if I don’t know what force my anchorage point will hold? • Minimize the arresting force Engineers need time to do their work – pre-planning is key!
9) Harness (and Body Belt) Inspection To inspect your harness or body belt, perform the following procedures. 1) WebbingGrasp the webbing with your hands 6 inches (152mm) to 8 inches (203mm) apart. Bend the webbing in an inverted “U” as shown. The surface tension resulting makes damaged fibers or cuts easier to detect. Follow this procedure the entire length of the webbing, inspecting both sides of each strap. Look for frayed edges, broken fibers, pulled stitches, cuts, burns and chemical damage. 2) D-Rings/Back PadsCheck D-rings for distortion, cracks, breaks, and rough or sharp edges. The D-ring should pivot freely. D-ring back pads should also be inspected for damage. 3) Attachment of BucklesInspect for any unusual wear, frayed or cut fibers, or broken stitching of the buckle or D-ring attachments. 4) Tongue/GrommetsThe tongue receives heavy wear from repeated buckling and unbuckling. Inspect for loose, distorted or broken grommets. Webbing should not have additional punched holes.
9)Harness (and Body Belt) Inspection To inspect your harness or body belt, perform the following procedures. 5) Tongue BucklesBuckle tongues should be free of distortion in shape and motion. They should overlap the buckle frame and move freely back and forth in their socket. Roller should turn freely on frame. Check for distortion or sharp edges. 6) Friction and Mating BucklesInspect the buckle for distortion. The outer bars and center bars must be straight. Pay special attention to corners and attachment points at the center bar. 7) Quick-Connect BucklesInspect the buckle for distortion. The outer bars and center bars must be straight. Make sure dual-tab release mechanism is free of debris and engages properly. AFTER FALL 8) Harness Fall Arrest Indicators Inspect fall arrest indicators (located on the back D-ring pad) for signs of activation. Remove from service if broken or stretched between any of the 4 pairs of arrows.
10) Lanyard Inspection When inspecting lanyards, begin at one end and work to the opposite end, slowly rotating the lanyard so that the entire circumference is checked. Additionally, follow the procedures below. 1) HardwareA) Snaps: Inspect closely for hook and eye distortions, cracks, corrosion, or pitted surfaces. The keeper (latch) should seat into the nose without binding and should not be distorted or obstructed. The keeper spring should exert sufficient force to firmly close the keeper. Keeper locks must prevent the keeper from opening when the keeper closes. B) Thimbles:The thimble must be firmly seated in the eye of the splice, and the splice should have no loose or cut strands. The edges of the thimble must be free of sharp edges, distortion, or cracks. 2) Wire Rope LanyardWhile rotating the wire rope lanyard, watch for cuts, frayed areas, or unusual wearing patterns on the wire. Broken strands will separate from the body of the lanyard. 3) Web Lanyard While bending webbing over a pipe or mandrel, observe each side of the webbed lanyard. This will reveal any cuts or breaks. Swelling, discoloration, cracks and charring are obvious signs of chemical or heat damage. Observe closely for any breaks in stitching.
10) Lanyard Inspection When inspecting lanyards, begin at one end and work to the opposite end, slowly rotating the lanyard so that the entire circumference is checked. Additionally, follow the procedures below. 4) Rope LanyardRotate the rope lanyard while inspecting from end-to-end for any fuzzy, worn, broken or cut fibers. Weakened areas from extreme loads will appear as a noticeable change in original diameter. The rope diameter should be uniform throughout, following a short break-in period. 5) Shock Absorber PackThe outer portion of the pack should be examined for burn holes and tears. Stitching on areas where the pack is sewn to D-rings, belts or lanyards should be examined for loose strands, rips and deterioration. 6) Shock-Absorbing LanyardShock-absorbing lanyards should be examined as a web lanyard (described in item 3 above). However, also look for the warning flag or signs of deployment. If the flag has been activated, remove this shock-absorbing lanyard from service.
11) Self-Retracting Lifeline Inspection 1) Check HousingBefore every use, inspect the unit’s housing for loose fasteners and bent, cracked, distorted, worn, malfunctioning or damaged parts. 2) LifelineTest the lifeline retraction and tension by pulling out several feet of the lifeline and allow it to retract back into the unit. Always maintain a light tension on the lifeline as it retracts. The lifeline should pull out freely and retract all the way back into the unit. Do not use the unit if the lifeline does not retract. The lifeline must be checked regularly for signs of damage. Inspect for cuts, burns, corrosion, kinks, frays or worn areas. Inspect any sewing (web lifelines) for loose, broken or damaged stitching 3) Braking MechanismThe braking mechanism must be tested by grasping the lifeline above the impact indicator and applying a sharp steady pull downward which will engage the brakes. There should be no slippage of the lifeline while the brakes are engaged, once tension is released, the brakes will disengage and the unit will return to the retractable mode. Do not use the unit if the brakes do not engage. Check the hardware as directed in 1A under Lanyard Inspection. The snap hook load indicator is located in the swivel of the snap hook. The swivel eye will elongate and expose a red area when subjected to fall arresting forces. Do not use the unit if the load impact indicator has been activated.
12) Harness and Lanyard Cleaning Basic care of all safety equipment will prolong the durable life of the unit and will contribute toward the performance of its vital safety function. Proper storage and maintenance after use are as important as cleansing the equipment of dirt, corrosives or contaminants. Storage areas should be clean, dry and free of exposure to fumes or corrosive elements. 1) Nylon or PolyesterRemove all surface dirt with a sponge dampened in plain water. Squeeze the sponge dry. Dip the sponge in a mild solution of water and commercial soap or detergent. Work up a thick lather with a vigorous back and forth motion; then wipe with a clean cloth. Hang freely to dry, but away from excessive heat. 2) HousingPeriodically clean the unit using a damp cloth and mild detergent. Towel dry. 3) DryingEquipment should dry thoroughly without close exposure to heat, steam or long periods of sunlight.
13) Utilization of a translation wagon in horizontal lifelines Safety lifeline with a special guiding system for lanyards. The use of 2 lanyards is not needed when passing the fixing point onto the structure With the attached system you need no supplementary guiding line
restraint 13) Utilization of a translation wagon in horizontal lifelines Double Safety lifelines with a special guiding system for lanyards. The use of 2 lanyards is not needed when passing the fixing point onto the structure With the attached system you need 2 lines, • one supporting line and • one system guiding line
13) Utilization of simple horizontal lifelines The use of 2 or a double lanyard is needed
2 1 3 4 14) Wearing a Full-Body Harness 14.1) Donning a Harness Full-body harnesses are the only form of body wear to be used for fall protection/fall arrest. It is very important to have a proper fitting harness throughout the entire course of a work shift. Do not allow your harness to become loose or slack. The following procedure will describe how to properly “don” (put on) a harness. The location of the chest, leg and sub-pelvic straps are critical to the optimal performance of a full-body harness in a fall arrest. (Refer to Proper Harness Fit section.) If chest, waist and/ or leg straps are buckled, release straps and unbuckle at this time. Hold harness by back D-ring. Shake harness to allow all straps to fall in place Pull leg strap between legs and connect to opposite end. Repeat with second leg strap. Connect waist strap, if present. Waist strap should be tight but not binding. Slip straps over shoulders so D-ring is located in middle of back between shoulder blades.
8 7 6 5 14.2) Wearing a Full-Body Harness Connect chest strap and position in mid-chest area 6” (152mm) to 8” (203mm) below the trachea but not below the sternum. Tighten to keep shoulder straps taut. After all straps have been buckled, tighten all webbing so that harness fits snug but allows full range of movement. Pass excess strap through loop keepers. To remove harness, reverse procedure. It is to recommends hanging the harness by back D-ring to help it keep its shape when not in use and provide the worker with a starting point when next attempting to don the harness.
14.3) Proper Harness Fit It is extremely important that your harness fits and is properly adjusted. Failure to do so can result in serious injury or death, and proper connection of both types of straps is essential to fall safety. After donning a harness, make sure to check: CHEST STRAP: Should be positioned in the middle of your chest [6” (152mm) to 8” (203mm) below the trachea but not below the sternum]. If the chest strap is positioned too high, the strap may move upwards during a fall arrest causing you to run the risk of strangulation. If the chest strap is too low or not connected at all, you could fall out of your harness during a fall. LEG STRAPS: Proper adjustment of the leg straps is critical for safety. Leg straps should be snug, but not snug to the point that they obstruct normal blood circulation in the legs. Failure to wear leg straps will not secure your body within the harness during a fall and could lead to serious injury or death. SUB-PELVIC STRAP: Provides support in the event of a fall, and also provides support when used for positioning. In a seated position, the sub-pelvic strap should comfortably provide a “seat” for the buttocks. In the event of a fall, simply lift up your legs to transfer weight to the sub-pelvic strap. Sub-Pelvic Non-Stretch Safety Harness Full Body Size is ideal for workers who must be suspended, raised or lowered to perform their jobs in confined spaces such as tanks, manholes, and pipes. Sub-Pelvic strap provides superior support in the buttocks area while relieving pressure from the shoulders and legs. In the event of a fall, the harness provides maximum force distribution, and the sub-pelvic strap adds comfort.
14.4) Donning a Pullover Front D-Ring Harness 1. Disconnect the leg strap buckles if they are connected. 2. Hold the harness by the back D-ring. Turn the harness so the front D-ring is facing you and the Miller strap is away from you. 3. Grasp shoulder straps directly below the front D-ring with both hands. Place your head through the center of the harness between the front and back D-rings. 4. Spin the harness 180 degrees so that the front D-ring is positioned in the front. 5. Slide one strap down over each arm so that the front D-ring rests in the mid-chest area and shoulder straps run vertically over the chest. 6. Pull leg strap between legs and connect to opposite end. Repeat with second leg strap. Adjust leg straps until snug. 7. Make adjustments to position the front D-ring properly by feeding webbing through the friction buckles. Adjust shoulder straps until snug. Pass excess strap through loop keepers. 8. To remove: Reverse procedure. Hang harness by back D-ring.
2 1 3 14.5) Buckle Connection Instructions SLOTTED MATING BUCKLE Pass the buckle with the center bar under the square link. Turn the center bar buckle so that the edges line up with the slots in the square link. Pull the center bar buckle completely through the square link and allow it to fall into place on top of the square link. Pull loose end of strap to tighten adjustment of the harness. Then slide rigid keeper (on chest strap only) up to buckle to reduce web sliding in buckle. Tuck excess webbing into elastic keepers. Ensure straps are not twisted. The loose end of webbing is for adjustment and must always be located on the outside (away from the user).
2 1 3 14.6) Buckle Connection Instructions QUICK-CONNECT BUCKLE To disconnect, push forward on both release levers, then pull buckle apart. Push both halves of the buckle together until you hear a click. Tug on both halves of the buckle to make sure it is firmly connected. Pull loose end of strap to tighten adjustment of the harness. Then slide rigid keeper (on chest strap only) up to buckle to reduce web sliding in buckle. Tuck excess webbing into elastic keepers. Ensure straps are not twisted. The loose end of webbing is for adjustment and must always be located on the outside (away from the user).
2 1 3 14.7) Buckle Connection Instructions TONGUE BUCKLE Pull the strap through until snug, placing the buckle tongue through the appropriate grommet. Tuck excess webbing into elastic keepers. Insert the loose strap of webbing through the tongue buckle from the underside.
14.8) Proper Use of D-Rings Shoulder D-rings Are for retrieval only. Side D-rings are for positioning only. Front D-rings are for positioning. Note front D-ring exception below. Back D-rings are for fall arrest or retrieval only
15) Rescue Plan • Work Scenarios vs. Rescue Scenarios • Different planning • Different equipment • Different skills • Do you plan for rescue at your facility? • Each time PPE is used, there must be a rescue plan! • You must be able to rescue someone in a minimum amount of time (<10 minutes). • Since irreparable damage may occur to the body in the first 10 minutes and statistics show that 50 % of the persons will have died if not rescued after 15 minutes, assure that a proper rescue solution is in place is of the utmost importance, since every minute counts. • Identify the Normal Conditions and Allowances. • Define the plan during the Hazard Identification and Risk Assessment, defining proper mitigation actions.
15) Rescue Plan: Harness Suspension Trauma • The Relief Step Safety Device alleviates the effects of orthostatic intolerance, also known as Harness Suspension Trauma. If a fall occurs, a person becomes suspended in a harness and remains both vertical and sedentary for a period of time, causing blood to “pool” in the veins of the legs. Subsequently, blood is restricted to the brain and other major organs that may initially result in unconsciousness. If not rescued promptly, serious injury or death may occur. The Relief Step is designed to provide a short-term solution for alleviating suspension trauma. • When used, the Relief Step Safety Device provides support and enhances blood circulation until rescue – permitting the ability to move and flex leg muscles • Small and lightweight; the Relief Step Safety Device attaches to any brand full-body harness • Utilizing two (2) Relief Steps (one for each leg/foot) assures greater comfort until rescue is completed
Questions (1/2) 1. When working at heights: as from which height do I have to use fall prevention of protection? • A. 4.0 m • B. 1.8 m • C. 2.5 m • D. When risk assessment indicates the risk of falling 2. When I work in a man-lift or ‘basket’: when must I be extra secured with proper Fall Protection Equipment? • A. If the basket is moving. • B. At all times. • C. Never. 3. If I work at heights and if I cannot use collective protective equipment (such as a scaffold for example), what are the minimum requirements for fall protection? • A. A safety belt and a lanyard. • B. A full body harness and a lanyard. • C. Any of the above.
Question (2/2) 4. If I work at heights and if I use collective protective equipment (as a scaffold for example), what are the minimum requirements for work platforms and scaffolding? • A. Complete floors, guardrails, toe boards and safe access and egress. • B. As determined by the maintenance inspector. • C. As determined by a competent scaffold erector. 5. I have to use a shock absorbing lanyard where the potential to fall is greater than: • A. 4 m • B. 7 m • C. 10 m