Introduction
“Ladders” serve as the essential footing supporting every industry, from manufacturing plants and construction sites to logistics warehouses. Although they are highly familiar tools used on a daily basis, a single misstep can directly lead to major fall or plummet accidents. In the field of occupational safety and health, keeping the proper positioning angle of a leaning ladder at 75 degrees (precisely around 75.1 degrees, generally recommended as 75 degrees) is considered an ironclad rule.
This article was written for safety managers, purchasing managers, and site supervisors working in the manufacturing, construction, and logistics industries within Vietnam. It clarifies the scientific and physical principles behind why angles like 70 or 80 degrees are unsafe, while explaining practical measurement techniques to verify a 75-degree angle on-site without any special equipment. Furthermore, it introduces case studies demonstrating how Hasegawa products, which comply with both Vietnamese National Standards (TCVN) and Japanese Industrial Standards (JIS), enhance workplace safety.
Challenges and Background of the “75-Degree” Angle in Ladder Setup
Market Data and the Reality of Fall Accidents
Among occupational accidents involving elevated work, falls and plummets from ladders and stepladders consistently account for a high percentage. According to occupational accident statistics in Japan, industrial accidents resulting in 4 or more days of absence caused by ladders or stepladders exceed 5,000 cases annually. It is reported that accidents due to an “inappropriate leaning angle” or “slipping of the base” account for approximately 35% of the total.
In Vietnam, alongside rapid economic growth, foreign-affiliated manufacturing plants, large-scale logistics warehouses, and construction projects are surging, making the reinforcement of Occupational Safety and Health (OSH) an urgent task. According to the annual occupational safety report by the Ministry of Labour, Invalids and Social Affairs (MOLISA), “falls from heights (ngã từ trên cao)” consistently rank among the top three causes of serious occupational accidents in the construction and manufacturing sectors. In particular, there are endless cases where site workers erect ladders based solely on “intuition,” resulting in the base slipping and causing a loss of balance. Given this background, the introduction of quantitative and objective safety standards is strongly demanded at the field level.
Two Critical Risks Caused by Angle Errors
1. When the Angle is Too Shallow (e.g., 60 Degrees or Less) = “Risk of Base Slipping”
When the ladder angle becomes too shallow, the vertical load applied to the ladder (the weight of the worker and cargo) is converted into a strong “horizontal component force” that pushes diagonally forward against the ground. The moment the coefficient of friction between the placement surface (ground) and the feet (the ladder’s rubber feet) falls below this horizontal component force, the base of the ladder slips violently outward. This is known as a “slipping phenomenon,” and workers are thrown to the ground before they can take any defensive posture.
2. When the Angle is Too Steep (e.g., 85 Degrees or More) = “Risk of Backward Tip-Over”
Conversely, if a ladder is placed against a wall at an angle close to vertical, when a worker climbs the ladder and leans slightly backward or lifts cargo, the center of gravity easily shifts outside (toward the back side) relative to the ladder’s fulcrum. As a result, a slight weight shift generates a “backward tip-over moment” (a force trying to flip backward), causing both the worker and the ladder to fall backward.
Based on physical calculations and ergonomic experiments, considering the shifting center of gravity of the human body when climbing, the approach when gripping the rungs with hands, and the frictional resistance of the placement surface, the golden ratio that is safest and most stable is “75 degrees.”
Implement on Site! Safe Ways to Measure “75 Degrees” and Practical Techniques
[Practice] The “Arm-Length Method” Requiring No Special Equipment
Understanding that site supervisors and workers may feel that “while a 75-degree angle is important, we cannot use a protractor every single time on-site,” we introduce the “Arm-Length Method.” This allows anyone to accurately recreate a 75-degree angle using only body parts without any tools. This method is widely recommended in Japanese JIS standards and international safety training.
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Basic Posture: Stand straight facing the front of the ladder that has been erected (at what is assumed to be an appropriate angle).
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Fixing the Feet: Place the tips of your safety shoes so they are in close contact with the left and right legs (bottom ends of the frame) of the ladder.
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Extending the Arms: Square your chest and extend both arms straight forward so they are horizontal to the ground.
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Judgment Criteria: At this point, if your palms can naturally and perfectly grip the rung (step) right in front of you, the angle of the ladder is almost accurately at “75 degrees.”
If your extended arms cannot reach the ladder, the angle is too shallow (less than 75 degrees); conversely, if your elbows must bend, the angle is too steep (exceeding 75 degrees). Since this can be performed in about 10 seconds as a pre-work inspection, it can easily be integrated into daily site routines.
Simple Calculation via the “4-to-1 Rule”
Another practical approach frequently used on architectural and construction sites is the “4-to-1 Rule (4:1 Rule).” This is a geometric approach that utilizes the ratio between the effective height of the ladder and the horizontal distance from the wall to the base of the ladder.
In the ratio of a right triangle, if the vertical height is set to “4” and the horizontal base is set to “1,” the resulting inclination angle becomes approximately 75.5 degrees.
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Specific Example: If the height from the ground to the contact point on the wall where the ladder leans is “4 meters,” place the base of the ladder “1 meter” away from the foot of the wall.
By keeping this ratio (4:1) in mind, anyone can easily calculate and position a ladder using a tape measure or visual estimation on-site.
Safe and Secure Elevated Work Solutions Provided by Hasegawa
Product Features to Visualize Safe Angles
Bringing together the expertise of Hasegawa Kogyo, which has led the Japanese scaffolding and ladder market for many years, “Hasegawa Vietnam” products come standard with various safety technologies to prevent human errors (careless mistakes or subjective misjudgments) on-site.
A prime example is the “Visual Angle Indicator (Angle Mark)” equipped on select models. Special labels or indicators designed to line up horizontally and vertically with the ground are placed on the side of the ladder frame. When leaning the ladder against a wall, simply checking with the naked eye that the mark is parallel to the ground automatically ensures that a 75-degree angle is secured.
Furthermore, to minimize the risk of slipping to the absolute limit, Hasegawa products place a thorough emphasis on the “feet (safety shoes made of elastomer/rubber material).” We have optimized the groove shape of the contact surface and the hardness of the rubber to maintain a high coefficient of friction even on epoxy floors common in Vietnamese factories, concrete floors at construction sites, or wet ground during rainy weather. Utilizing the highest quality materials, they offer excellent oil and wear resistance, and are resistant to hardening even after long-term use.
Case Study in a Japanese Manufacturing Plant in Vietnam
Here, we would like to share an improvement case study from a major Japanese automotive parts manufacturing plant located in Binh Duong Province, Vietnam.
【Before: Challenges Prior to Implementation】
At this factory, inexpensive commercial aluminum ladders procured locally were used for equipment maintenance and piping inspections. Although the site workers had received safety training, they often erected ladders based on intuition due to rushing their work, and frequently climbed up and down when the angle was around 60 degrees. One day, due to a small amount of machine oil adhering to the floor surface, the base of a ladder slipped, causing a worker to fall from a height of about 2.5 meters. Fortunately, it did not lead to a major injury, but the accident resulted in a 3-day absence from work, forcing the factory’s Safety Officer to take drastic countermeasures.
【Action: Hasegawa’s Improvement Approach】
The Safety Officer consulted with Hasegawa Vietnam and decided to completely replace all ladders in the factory with “Hasegawa Professional Aluminum Ladders,” which are JIS-compliant and feature 75-degree angle marks. Concurrently, Hasegawa’s Japanese specialists and local Vietnamese staff visited the factory to conduct a free practical seminar on “Proper Ladder Use and the Arm-Length Method for 75 Degrees” targeting all maintenance workers. On the walls of the workspace, safety posters in Vietnamese reading “Set up ladders using the 4:1 rule” were displayed.
【After: Effects Post-Implementation】
Following implementation, a culture where all workers check for 75 degrees using the “Arm-Length Method” before starting work took root. Thanks to the synergistic effect of the robust feet, the rigid frame structure of the Hasegawa ladders, and the precise setup angle, the number of slipping and falling accidents caused by ladders has remained at “zero” for the two years that have passed since introduction. Workers have also highly praised the change, noting: “The ‘twisting’ or shaking of the ladder when climbing has completely disappeared, allowing us to focus on our work with peace of mind. As a result, inspection efficiency has improved by 15%.”
Reliability and Support System of Hasegawa Vietnam
Quality Control and Compliance with International and National Standards
Products provided by Hasegawa Vietnam not only clear strict Japanese JIS standards (such as JIS S1121 for aluminum alloy ladders) but also fully satisfy international safety criteria and the requirements of Vietnamese National Standards (TCVN).
At Hasegawa Vietnam’s own factory in Dong Nai Province, a rigorous quality control system equivalent to that of factories in Japan is implemented. We thoroughly manage lots across all processes, from the receiving inspection of aluminum alloy raw materials (such as A6063, which is lightweight and high-strength) to non-destructive testing of weld strength and severe load testing on finished products (load testing at several times the maximum user weight). This promises overwhelming sturdiness and reliability, drawing a clear line against low-priced products of unknown origin circulating in the local market.
Local Customization and Support System
Work sites in Vietnam vary widely in terms of factory layout, equipment height, and floor conditions. Hasegawa Vietnam can respond quickly to specific, unique on-site needs, such as “Standard sizes cannot reach the factory’s piping” or “We want to attach custom hooks to use it safely at 175 degrees in narrow corridors.”
Because we possess our own production base and an experienced engineering team within Vietnam, we handle everything from design and prototyping to manufacturing and delivery as a one-stop solution with a speed that reflects Japanese quality. In addition, our after-sales support system is fully established, including advice on periodic inspection methods after purchase and supplying replacement parts like rubber feet that wear out over time. We are not merely a manufacturer selling goods; we are a partner building a “Safe Footing” together for everyone working in Vietnam.
Conclusion
The ladder leaning angle of “75 degrees” is not just a dry number in a manual, but a “scientific boundary of safety” derived to protect workers’ lives from slipping or backward tip-overs. To prevent site safety management from becoming a mere formality, it is essential that individual workers master practical techniques like the “Arm-Length Method” or the “4-to-1 Rule” and reliably execute them during daily inspections.
At the same time, to maximize the potential of that “75 degrees,” selecting a reliable work tool equipped with a rigid frame free of distortion and high-quality feet that firmly grip the floor surface is indispensable. Fusing Japanese quality standards (JIS) with Vietnamese on-site needs (TCVN), Hasegawa Vietnam stands ready to fully support the reduction of industrial accident risks at your factory.
Safety managers and purchasing managers who feel even the slightest challenge regarding safety measures for elevated work are welcome to contact Hasegawa Vietnam at any time. We are always available to propose the most suitable equipment for your site conditions and discuss safety training sessions.