Safeopedia Explains Impact Resistance
Impact is one of the basic hazard categories and a common one across many jobs and work tasks.
For instance, when a construction worker falls off the edge while wearing fall protection gear, their body harness, lifeline, self-retracting lanyard, and anchor are all subject to high impact. Unless each of those components can withstand the force of the impact, the PPE cannot ensure the worker’s safety. Likewise, safety glasses can only protect a worker’s eyes from a projectile if it can withstand its impact.
While the inherent qualities of the material play a large role in determining its level of impact resistance, environmental conditions can also affect the amount of energy it is capable of absorbing. Colder temperatures, for instance, make a material more brittle and reduces its ability to withstand the force of an impact.
In addition to the protection it provides, impact resistance is also a factor in a material’s durability.
OSHA Standards for Impact Resistance
The Occupational Safety and Health Administration (OSHA) has issued a number of standards that touch on impact resistance for different categories of PPE.
Eye and Face Protection
OSHA 1910.133 provides general requirements and criteria for eye and face protection.
According to the standard, employers must ensure that every employee exposed to any hazard to the eye or face from flying particles, chemicals, acidic or caustic liquids, gasses and vapors, or dangerous radiation is provided with adequate face and eye protection. In many cases, this will include PPE that provides some level of impact resistance.
Safety glasses can be made with impact-resistant metal or plastic frames and fitted with impact-resistant lenses. According to OSHA 1910.133(b)(1), eye and face protection equipment must comply with one of the following consensus standards:
Likewise, safety goggles can provide impact protection while creating a full seal around the eye to protect it from dust, liquid splashes, and other hazards.
Hand Protection
OSHA 1910.138 requires that employers provide appropriate hand protection for employees whose hands will be exposed to hazards.
Workers’ hands can be particularly vulnerable to impact injuries, which can damage muscles, ligaments, and tendons. To guard against these hazards, workers can wear safety gloves equipped with dorsal (back of the hand) impact protection.
Head Protection
OSHA 1910.135 outlines general requirements and criteria for head protection. Employers must provide adequate head protection whenever there is a potential for injury from falling objects or impact to the side of the head. Both Type I and Type II hard hats provide impact protection to the wearer.
1910.135(b)(1) states that head protection must comply with one of the following consensus standards:
Foot Protection
OSHA 1910.136 provides general requirements for protective footwear. Employers must mandate the right type of footwear based on the hazards of the job. This can include impact protection if there is a risk of objects falling on, rolling over, or crushing the foot.
Steel-toed shoes or boots (or footwear with toe caps made of other materials) are effective in protecting the most vulnerable portions of the foot from impact-related injuries. Metatarsal guards made of aluminum, steel, or plastic can also be strapped to the outside of the shoe or boot to provide additional impact protection.
According to OSHA 1910.136(b)(1), protective footwear must comply with at least one of the following consensus standards:
Safety Nets
OSHA 1926.105 mandates the use of safety nets in construction projects where there is a risk of falling from a height of 25 feet or more. The nets must extend 8 feet beyond the edge of the work surface (if the vertical drop distance is 5 feet or less) and as close under it as possible. Safety hooks or shackles used to fasten the net to its support must be made of forged steel.
Safety nets must be able to withstand the impact of a falling worker. To ensure that it can, every safety net is drop tested after installation. This involves dropping a 400 pound sandbag onto the net from the highest elevation from which a worker could fall.
Personal Protective and Life-Saving Equipment for Construction
Requirements for fall protection systems can be found in 1910.140. OSHA also specifies tensile load criteria for various components of a PFAS:
- Vertical lifelines and lanyards shall have a minimal tensile strength of 5,000 pounds (22.24 kN) – 1915.159(b)(2)
- Self-retracting lifelines and lanyards that automatically limit free fall distances to 2 feet (0.61 m) or less shall be capable of sustaining a minimal tensile load of 3,000 pounds (13.34 kN) with the lifeline or lanyard in the fully extended position – 1915.159(b)(3)
- Self-retracting lifelines and lanyards that do not limit free fall distance to 2 feet (0.61 m) or less, ripstitch lanyards, and tearing and deforming lanyards shall be capable of sustaining a minimal static tensile load of 5,000 pounds (22.24 kN) applied to the device in the fully extended position – 1915.159(b)(4)
- D-rings and snap hooks shall be capable of sustaining a minimum tensile load of 5,000 pounds (22.24 kN) – 1915.159(a)(3)
- D-ring and snap hooks shall be proof-tested to a minimum tensile load of 3,600 pounds (16 kN) without cracking, breaking, or being permanently deformed – 1915.159(a)(4)
- Anchor points for PFAS should be capable of supporting at least 5,000 pounds per employee.
Testing and Certification of Impact Resistant PPE
PPE testing ensures that the equipment meets the requirements of all applicable standards, is safe to use, and will protect the wearer as intended.
Impact-Resistant Gloves
ANSI/ISEA 138-2019 outlines minimum performance, classification, and labeling requirements for products designed to protect the fingers and knuckles from impact forces.
This standard provides three impact resistance levels for gloves:
- Performance Level 1: Able to absorb up to 11.3 kN
- Performance Level 2: Able to absorb up to 8.1 kN
- Performance Level 3: Able to absorb up to 5 kN
Impact-Resistant Eye and Face Protection
ANSI Z87.1 details testing procedures for safety glasses, safety goggles, welding goggles, masks and face shields that protect against impact injury.
Impact tests include:
- Drop Ball Test: A one-inch steel ball is dropped on the eyewear from a height of 50 inches
- High Mass Impact Test: A 500g projectile with a pointed end is dropped no the eyewear from a height of 50 inches
Eye protection products marked as impact protectors Z87+ indicates that they have passed these high-impact testing requirements.
Head Protection
Type I hard hats provide impact resistance at the top of the head and are designed to protect against injuries from falling objects. Type II hard hats also protect the sides of the head.
ANSI Z89 specifies design, functionality, testing, and certification required for head protection. Impact testing is done under two conditions:
- Hot Temperature: At 120°F (49°C) or higher
- Cold Temperature: At 0°F (-18°C) or lower
Under both conditions, an 8 pound steel object is dropped on the hard hat to measure how much of the impact energy it absorbs.
Foot Protection
Safety shoes must conform to various safety standards by ASTM, ANSI, and OSHA.
Compliant footwear is tested for impact resistance by dropping a weighted object from a height of one foot. Based on the test outcomes, it is then rated for one of three impact resistance levels:
- ASTM F2413 I/75: Impact protection up to 75 pounds
- ASTM F2413 I/50: Impact protection up to 50 pounds
- ASTM F2413 I/30: Impact protection up to 30 pounds
A similar rating is given for metatarsal protection, labeled “Mt” rather than “I”:
- ASTM F2413 Mt/75: Impact protection up to 75 pounds
- ASTM F2413 Mt/50: Impact protection up to 50 pounds
- ASTM F2413 Mt/30: Impact protection up to 30 pounds
Selecting Impact Resistant PPE
Most construction and industrial jobs put workers at risk of injury from flying shards, dropped objects, and heavy tools. Depending on the particular hazards they encounter, workers will need different types of PPE that offer some level of impact resistance.
Selecting the right impact-resistant PPE will require a consideration of various factors. For example, impact-resistant gloves come in a variety of materials, each with unique properties:
- Foam: Weak impact resistance and breaks down after extended use and exposure to chemicals or the elements
- Gel: Allows for more flexibility but can also break down after extended use
- Silicone: Does not provide a high level of impact resistance but is a great option for gloves that also need to be flame- or heat-resistant
- Polycarbonate: A hard material that has to be molded around the knuckles – used primarily in the military and law enforcement
- Thermoplastic Rubber (TPR): Provides excellent impact protection and a high level of dexterity – widely used for manufacturing impact-resistant gloves
Coverage matters, too. For example, safety shoes with impact-resistant toe caps might offer very little metatarsal protection. It’s important to make sure that the PPE offers protection to every part of the body that is at risk of impact.
Like all other PPE, comfort, dexterity, and compatibility with other safety equipment should also be taken into consideration.
Maintenance and Inspection
All PPE should be inspected before and after each use for signs of wear or damage. A closer, more detailed inspection should take place each month to ensure that the PPE is still in good shape. If you notice any signs of the defect, the item should be removed from use immediately and replaced.
After use, the PPE in a clean, dry place to extend its useful life. Keep it away from heat, dust, and direct sunlight if possible, as these can wear down materials more quickly and compromise their effectiveness.
PPE that is used regularly should be inspected periodically by authorized safety inspectors and serviced according to the manufacturer’s instructions. The frequency of these inspections will depend on the type of equipment. Full-body harnesses, for instance, must be inspected by a competent person every six months. Type 1 fall arrest devices must be inspected every three months. Type 2 and 3 devices like self-retracting lifelines, anchors, pulleys, and tripods need to be inspected every 12 months.
Training and Awareness
Employers must provide training for all employees who will be using impact-resistant PPE.
Training sessions should cover:
- The importance of impact-resistant PPE for preventing injuries
- The limitations of impact-resistant PPE
- How to use the PPE correctly
- Proper storage and maintenance
- How and when to inspect each item
It’s also advisable to supplement this training with occasional toolbox talks about impact-resistant PPE and how to use it properly.
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