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The XXXV

Annual International Occupational Ergonomics and Safety Conference

Munich, Germany

October 9-10, 2023

ISBN: 9781938496615 62

DOI: https://doi.org/10.47461/isoes.2023.brickman

Residential Bunk Bed Child Entrapment Safety Test Methods

Dennis B. Brickman

, Joseph P Mohorovic

, Anne C. Mathias

, and Erick H. Knox

Engineering Systems Inc., 4215 Campus Drive, Aurora, Illinois 60504

Corresponding author's Email: dbbrickman@engsys.com

Abstract: A human factors accident reconstruction was conducted to analyze the circumstances surrounding a residential

consumer bunk bed death involving a two-year-old boy who became trapped between the upper bunk and the top rung of the

ladder. An anthropomorphic child dummy and an ASTM bunk bed standard child torso test probe were used to analyze the

flexibility of the bunk bed ladder brackets and the gap between the brackets and the upper bed frame that allowed the ladder to

lift and tilt, creating a child entrapment hazard. The primary goal of this investigation is to identify alternative safety test

methods and designs to reduce the risk associated with these types of injuries and to make consumer bunk bed designers,

manufacturers, distributors, sellers, safety standard agencies, testing laboratories, furniture industry associations, consumer

safety organizations, pediatricians, and users more aware of the bunk bed ladder tilting/repositioning child entrapment danger.

Keywords: Residential Bunk Bed, Child Entrapment Hazard, Safety Test Methods

1. Literature Review

Injuries associated with young children becoming entrapped between a residential bunk bed side ladder and the bed

have been reported in the ergonomics in design literature (Pollack-Nelson, 2011). To further address child entrapment hazards

between the ladder and the lower bunk bed structure in the United States, changes were made to the performance requirements

of ASTM F1427 Standard Consumer Safety Specification for Bunk Beds in 2013 (U.S. CPSC, 2015). A new section titled

Mattress Size and Fit (Lower Foundation) was added to the ASTM F1427-13 standard to address entrapment hazards between

the mattress and additional components, such as a ladder, attached to the lower bunk. A corresponding section was also added

to the Test Methods section of the ASTM F1427-13 standard to prescribe how to measure the gap between a mattress and an

adjacent rigid structural component. The requirements for testing of openings in the lower bunk using the wedge block for

neck entrapment were expanded from end structures to the entire boundary of the lower bunk. The section titled Ladders was

expanded to address entrapment hazards in and around ladders by prescribing a testing procedure involving the use of the

wedge block probe (simulating a child’s torso) and the 9-inch diameter rigid sphere to gauge gaps in the bed structure (ASTM

F1427, 2013).

Performance requirements to address entrapment hazards are also included in the international bunk bed safety

standards (AS/NZS 4220, 2010; EN 747-1, 2015). European EN 747-1:2015 standard for bunk beds contains safety

requirements for accessible gaps between the bunk bed ladder tread and any part of the bed frame (EN 747-1, 2015).

Australia/New Zealand AS/NZS 4220:2010 standard for bunk beds includes a test method for the integrity of the ladder/access

device attachment means on a bunk bed where specified forces are applied to dislodge the ladder/access device from its

attachment position (AS/NZS 4220, 2010).

Consumer bunk bed inclined ladders are typically attached to the top bed rail by hooks positioned at the top of the

ladder as shown in ASTM F1427-13 (ASTM F1427, 2013). However, the international patent literature discloses an invention

for a bracket for mounting a bunk bed ladder from the bed rail of an upper bunk to prevent the ladder from tilting outward

while climbing (Fredman, 1982). An objective of the Fredman patent invention is to provide a bracket structure for mounting

a ladder on a bunk bed assembly which prevents the ladder from tilting outward and reduces ladder failure due to forces exerted

when climbing the ladder, such as occurs when the ladder is attached to the bed rail by conventional hooks.

2. Residential Bunk Bed Child Entrapment Incident

On May 22, 2018, a two-year-old boy became trapped in a tight space between a consumer bunk bed upper bunk and

the top rung of the ladder at his residence in Ohio. The two-year-old child’s mother found her son facing away from the bunk

bed with his torso against the ladder top rung, his head above the ladder top rung, and his feet below the ladder top rung. The

The XXXV

Annual International Occupational Ergonomics and Safety Conference

Munich, Germany

October 9-10, 2023

Figure 1. Incident Bunk Bed (Child Entrapment Gap Indicated by Red Oval)

Figure 2. Deformed Bunk Bed Ladder Bracket After Incident

The XXXV

Annual International Occupational Ergonomics and Safety Conference

Munich, Germany

October 9-10, 2023

Figure 3. Anthropomorphic Child Dummy Trapped in Gap Between Ladder Top Rung and Upper Bunk Structure

mother tried to pull her two-year-old child through the space between the upper bunk structure and the ladder top rung to free

his trapped body. The child’s body was tightly wedged and would not move. During the child’s extraction from the bunk bed,

the child’s mother pulled on the child’s body, the ladder moved and one of the ladder top metal brackets broke, and eventually

the child’s body released from the entrapment.

Figure 1 shows the subject bunk bed involved in the incident with the child entrapment gap indicated by the red oval.

When the ladder feet are contacting the floor, there is a 2.1-inch (53.3 mm) gap between the ladder top rung and the upper bunk

structure. The ladder is hooked onto the upper bed frame, and the two ladder metal hooks are attached to the upper bunk

structure with screws. Figure 2 depicts the condition of the subject bunk bed ladder deformed brackets after the incident.

3. Accident Reconstruction

A systematic accident reconstruction method incorporating human factors and biomechanics (Knox, 2015) was

performed and included using the subject bunk bed and an anthropomorphic child dummy to analyze how the child became

entrapped during the incident. Figure 3A (left image) displays the anthropomorphic child dummy with its feet and lower legs

situated in the gap between the ladder top rung and the upper bunk structure. While the ladder feet were on the floor, the gap

between the ladder top rung and the upper bunk structure was too small for the dummy to enter (see arrows in Figure 3A).

However, during the accident reconstruction, tilting of the ladder increased the gap between the ladder top rung and the upper

bunk structure such that the anthropomorphic child dummy lowered into the gap. Figure 3B (right image) displays the

anthropomorphic child dummy’s torso trapped between the ladder top rung and the upper bunk structure in a similar position

as described by the child’s mother after the incident.

4. Testing

Tilt testing conducted using an exemplar ladder on the subject bunk bed indicated that the ladder began to lift from

the floor at approximately 0.8 pounds of force applied at the ladder base. With the application of 7 pounds force to the exemplar

The XXXV

Annual International Occupational Ergonomics and Safety Conference

Munich, Germany

October 9-10, 2023

Figure 4. Exemplar Ladder Contacting Floor (Left Image) and Tilted (Right Image)

Figure 5. ASTM F1427 Test Wedge Pulled Through Exemplar Ladder

ladder base, the ladder tilted enough to increase the top opening enough to allow passage of the ASTM F1427 torso test wedge

(3.5 inches / 88.9 mm). Figure 4 shows an exemplar ladder in a position contacting the floor (left image) and in a tilted position

(right image). Figure 5A (left image) illustrates how the ASTM F1427 test wedge does not pass between the ladder top rung

and the upper bunk structure from below with the ladder base contacting the floor. Figure 5B (right image) depicts the ASTM

F1427 test wedge completely passing through the gap from below the gap with the ladder tilted after approximately 43 pounds

force was applied to the test wedge.

5. Safety Standards Analysis

Based upon the test results from the exemplar ladder, the bunk bed involved in the subject incident failed to comply

with the ASTM F1427-13 safety standard ladder requirements with respect to ladder repositioning or tilting, and complete

The XXXV

Annual International Occupational Ergonomics and Safety Conference

Munich, Germany

October 9-10, 2023

passage of the test wedge between the ladder top step and upper bunk boundary (ASTM F1427, 2013). Specifically, the incident

ladder did not meet the requirements of ASTM F1427-13 section 4.9.1, which states that the ladder shall be attached in a

manner that prevents inadvertent disengagement, repositioning, or tilting while in use. Also, the incident ladder failed to

comply with the requirements of ASTM F1427-13 section 4.9.3, which states that there shall be no openings between the ladder

step and the upper bunk boundary that allow complete passage of the wedge block unless they are large enough to permit the

free passage of the 9-inch (230 mm) diameter rigid sphere. The flexibility of the ladder brackets and the gap between the ladder

brackets and the upper bed frame allowed the ladder to lift and tilt, which permitted complete passage of the wedge block.

Furthermore, the gap between the upper bunk structure and the non-tilted ladder top rung (2.1 inches / 53.3 mm) did not meet

the requirements of EN 747-1:2015, which specify that the gap between any tread and any part of the bed frame shall be: a)

less than 7 mm (0.28 inch); or b) at least 12 mm (0.47 inch) but not more than 25 mm (0.98 inch); or c) at least 60 mm (2.35

inches) but not more than 75 mm (2.95 inches); or d) at least 200 mm (7.87 inches).

6. Conclusions

Human factors analysis determined that children as young as two years of age will be capable of exerting enough force

on the incident bunk bed ladder to create a potentially hazardous gap between the ladder top rung and the upper bunk structure

(Brickman, 2002). Following the subject incident, the U.S. Consumer Product Safety Commission (CPSC) independently

identified that the metal hook fastening the ladder to the top bunk bed frame can move away or detach from the bed frame

when the ladder is lifted, causing the gap between the ladder step and bed frame to open wider than 3.5 inches (88.9 mm),

posing serious child entrapment and strangulation hazards (U.S. CPSC, 2021). After the incident, the subject bunk bed

manufacturer recall provided consumers with a retrofitted and reinforced ladder bracket to inhibit the repositioning and tilting

of the ladder, which creates the serious child entrapment hazard (U.S. CPSC, 2021).

The primary goal of this investigation is to identify alternative safety test methods and designs to reduce the risk

associated with these types of injuries and to make consumer bunk bed designers, manufacturers, distributors, sellers, safety

standard agencies, testing laboratories, furniture industry associations, consumer safety organizations, pediatricians, and users

more aware of the bunk bed ladder tilting/repositioning child entrapment danger. An industry survey revealed that there exist

alternative residential consumer bunk bed designs that do not possess the gap child entrapment hazard between the ladder top

rung and the upper bunk boundary (Julian Bowen Limited, 2014; Storkcraft, 2019). The present study showed that the current

ASTM F1427-19 Standard Consumer Safety Specification for Bunk Beds (ASTM F1427, 2019) can be improved regarding

the definition of ladder tilting/repositioning, specific dimensional requirements for the gap between the ladder top rung and

upper bunk based on anthropometric child data, and ladder tilting test methods and requirements.

7. References

AS/NZS 4220. (2010). Bunk Beds and Other Elevated Beds.

ASTM F1427. (2013). Standard Consumer Safety Specification for Bunk Beds.

ASTM F1427. (2019). Standard Consumer Safety Specification for Bunk Beds.

Brickman, D.B. (2002). Standard Infant Crib Testing Enhanced with Live Child Shaking. Proceedings of IMECE2002 ASME

International Mechanical Engineering Congress & Exposition, IMECE2002-32460, 1-8.

EN 747-1. (2015). Furniture – Bunk Beds and High Beds – Part 1: Safety, Strength and Durability Requirements.

Fredman. (1982). Bunk Bed Ladder Bracket. Canada Patent CA1122752A.

Julian Bowen Limited. (2014). Domino Bunk Bed Assembly Instructions.

Knox, E.H. et al. (2015). Methods of Accident Reconstruction: Biomechanical and Human Factors Considerations. Proceedings

of the ASME 2015 International Mechanical Engineering Conference and Exposition, IMECE2015-53666, 1-11.

Pollock-Nelson, C. (2011). Fatality in the Side of a Bunk Bed. Ergonomics in Design, 9-11.

Storkcraft. (2019). Caribou Bunk Bed Model 09720-12-LB.

U.S. CPSC. (2015). CPSC Staff’s Opinion of Changes to ASTM F1427, Standard Consumer Safety Specification for Bunk

Beds, from a Mechanical Testing Perspective.

U.S. CPSC. (2021). CPSC Recall Number 22-036.