Know Your Netting
For maximum protection, use both a netting system and a personal horizontal lifeline for employees.
- By Dave Thomas
- Mar 01, 2006
IN the construction industry, workers are consistently operating in environments where hazards abound. Employers and employees alike rely on state-of-the-art fall protection equipment as they work on various types of structures. With all of the different options for fall protection, it is important to take a look at netting systems.
Netting assures workers they can safely and efficiently do their job, day after day. As a group of five workers in Charleston, S.C., learned, netting can quickly save a life. These particular workers were constructing the Cooper River Bridge when a 4-ton piece of tower wall fell 160 feet. Although the debris netting system being used was designed only to catch a construction worker and/or smaller objects, it miraculously held 8,000 pounds as the workers below got out from underneath the netting.
The falling portion of tower wall not only would have crushed the five employees, but also would have destroyed a part of the unfinished concrete roadway 300 feet below the bridge, thus costing lives, time, and money.
The Need for Netting
As any contractor knows, every possible opportunity should be taken to protect the employees working on a project and civilians below. It is also of great importance to protect the buildings adjacent to the structure and the project being constructed.
According to OSHA, falls are the leading cause of worker fatalities within the construction industry. Between 150 and 200 workers are killed and more than 100,000 are injured annually as a result of falls at construction sites. Because of these high numbers, fall protection is necessary and required any time a fall injury is possible. Besides the threat to life, the damage to buildings and tools is a costly error that can be easily avoided.
Many options are available for contractors to keep their employees safe while working where height is a risk factor. A netting system is one of the most reasonable ways to ensure the safety of both people and equipment. Many different types of nettings exist, allowing contractors to choose one or a combination to best fit the needs of their situation. These netting choices will save the lives of employees; they also protect those on the ground from falling tools, materials, or other debris. These systems can be reused if they are properly cared for, installed, and inspected.
When choosing a netting system, often the determining factor is not the type of project being constructed. Although that's important, the main consideration should be the types of resources you are trying to protect. If you're mainly concerned about containing debris and setting up a visible guardrail, a vertical netting system fulfilling all OSHA requirements should suffice. If the safety goals consist of providing fall protection to personnel and catching falling debris, a perimeter netting system is necessary to meet safety requirements.
To choose a perimeter netting system, whether for debris or for personnel, one must consider the standards OSHA has established for determining the appropriate size. Safety nets must be installed as close as practicable under the walking surface on which employees are working. A walking/working surface is defined by OSHA as any surface, whether horizontal or vertical, on which an employee walks or works, including but not limited to floors, roofs, ramps, bridges, runways, formwork, and concrete reinforcing steel. Walking/working surfaces do not include ladders, vehicles, or trailers on which employees must be located to perform their work duties. Perimeters should never be located more than 30 feet below the walking/working level they are installed to protect.
Also, OSHA standards state that safety nets must be installed with sufficient clearance underneath to prevent contact with the surface or structure below. When nets are used on bridges, the potential fall area from the walking/working surface to the net shall be unobstructed. Some guidelines exist for determining the distance a safety net must extend from the work surface. If the vertical distance from the working level to the horizontal plane of the net surface is 5 feet or less, the net must extend out 8 feet (or 2.4 meters). If the vertical distance is more than 5 feet but less than 10 feet, the minimum required distance from the outer edge of the net to the edge of the working surface is 10 feet. Finally, if the vertical distance is more than 10 feet, the horizontal distance of the net should be 13 feet.
Vertical Netting Systems
The first type of netting to discuss is a vertical net debris containment system. These offer many benefits. Vertical nets increase safety by preventing debris from falling on the public and adjacent properties below. Vertical netting is usually recognized by its bright orange color. The netting can protect workers near leading edges by serving as a guardrail system, eliminating the need for a mid-rail and toe board if it meets certain OSHA standards. If the netting is purchased in a bright color, it provides a visible safety barrier that is easily seen from ground level.
Vertical netting can serve as a temporary partition for crowd control or demolition. This netting also can be used around perimeters, as well as in holes and unprotected sides and edges. Because this type of netting is easy to install, remove, relocate, and store, it cuts down on the amount of time needed for preparation and produces greater worker productivity. A vertical net system can be one of the most complete and cost-effective options for debris containment available.
Most vertical netting systems are installed using a cable. The standard height needed for construction work is determined by city ordinances. OSHA requires vertical netting to be 42 inches plus or minus 3 inches above the walking/working level. City ordinances also have netting requirements, so consult them before choosing a specific height. Most require a 48-inch height; however, Chicago and New York City both require vertical netting to be 60 inches or taller. To secure netting, attach by clips to a wire cable at the top edge. The bottom of the netting can be secured by plates that fasten directly to the walking/working level of the structure.
When choosing a vertical netting debris containment system, it is important to make sure it complies with OSHA requirements. If you're using a vertical netting system as a guardrail, remember that, according to OSHA 1926.500 (b)(3), guardrail systems shall be capable of withstanding, without failure, a force or at least 200 pounds applied 2 inches from the top edge, in any outward or downward direction, at any point along the top edge.
To reuse a vertical netting system, the nets should show no evidence of damage. Also, any piece of equipment (clips or tie down plates) should show no sign of damage.
Perimeter Debris Netting Systems
Netting systems also exist to catch debris and, in some cases, workers. Known as a perimeter net system, this netting works to protect the public and properties below work areas that are threatened by falling debris. This netting is often designed to catch job site debris at concrete building construction sites from the pour level and during the installation and removal of tables or forms. It can catch bricks, concrete blocks, hand tools, and general construction debris.
Some systems meet ANSI and OSHA standards to provide fall protection from the working surface or the floor on which the system is mounted. A perimeter debris netting system must be capable of absorbing an impact force of a drop test consisting of a 400-pound bag of sand 30 inches in diameter that is dropped from the highest walking/working level being protected. Any item that the safety net catches must be removed as soon as possible (at least before the next work shift).
This netting can be attached to the appropriate level where needed by using clamps. A pole extends upward from the clamps, providing suspension for the poles extending out horizontally from the building. Each system can be reused as long as it is inspected for damage before each use. Another benefit of these systems is that they can be moved up to other floor levels as construction progresses. This is a viable netting solution that provides security and safety to workers, the public, and equipment.
Passive Fall Protection vs. Active Fall Protection
All netting systems are known as passive, or barrier, fall protection. By definition, once a netting system is properly installed, it will protect all workers and equipment within a defined area. However, if a safety net (whether vertical or horizontal) is not rated as a personal fall arrest system, use of lifelines may be necessary.
OSHA defines a lifeline as a component consisting of a flexible line for connection to an anchorage at one end to hang vertically (vertical lifeline) or for connection to anchorages at both ends to stretch horizontally (horizontal lifeline) and that serves as a means for connecting other components of a personal fall arrest system to the anchorage. For the highest level of protection, employers and contractors should employ both a netting system and a personal horizontal lifeline for employees.
Rarely is securing a perimeter for falling debris and personnel the only method of fall protection when working on a construction project. A number of other obstacles usually exist, including (but not limited to): elevator shafts, window or door frames, skylights, holes, and openings. A hole is defined as any void or gap 2 inches or more in the least dimension in a floor, roof, or other walking/working surface. An opening is a gap or void 30 inches or more in height and 18 inches or more wide in a wall or partition through which employees can fall to a lower level.
Vertical netting systems can serve as guardrails around these, and personnel netting systems can be installed beneath them for limited fall protection. However, safety is ensured when a lifeline is added to the equation. Horizontal and vertical lifelines are easy to use and assemble and can save lives. They also can be reused if inspected before each use to ensure no damage has occurred to the product.
Choosing the Right Netting and Fall Protection
The most important thing to remember when choosing the type of netting and fall protection to use at your job site is that all projects are unique, so different types of fall protection can be used to achieve the highest level of protection. It may be helpful to consult with a professional safety distributor or netting manufacturer. Suppliers and distributors with extensive experience in netting safety solutions will evaluate each individual project and let you know what type of protection will offer the best safety plan for you and your employees.
Some companies have developed adjustable personnel and debris net systems that are rated for complete fall protection. Suppliers and distributors can help to make sure the equipment you purchase meets all of the necessary safety standards to ensure a safe and productive project from beginning to end. They will let you know how your fall protection plan and equipment can evolve as you change elevations and incorporate new technologies.
This article appeared in the March 2006 issue of Occupational Health & Safety.
This article originally appeared in the March 2006 issue of Occupational Health & Safety.