Glovebox reach differs from normal workstation reach because the operator's arms pass through fixed gloveports. The position and geometry of these ports, the depth of the enclosure and the position of the work can restrict shoulder and elbow movement and determine the posture required to perform a task.
Frequently performed or precision work should therefore be positioned with consideration of the operator's natural working reach rather than simply placed wherever space is available inside the enclosure.
A useful ergonomic principle is to keep frequently performed work close to the operator and within a comfortable range of arm movement.
In the publicly released LANL paper Balancing Dose Reduction from Shielding and the Impact on Workplace Ergonomics, the primary work zone is described as approximately the length of the forearm.
The LANL ergonomics team recommends that main glovebox work activities are kept within approximately 22 in (559 mm) of the worker's body. The paper describes this as the secondary work zone and notes that it is usually within approximately 18 in (457 mm) from the front of the gloveport.
Source: Mann, J., Linn, J., Chan, M. and Hetrick, L., Balancing Dose Reduction from Shielding and the Impact on Workplace Ergonomics, Los Alamos National Laboratory, LA-UR-20-22703.
Increasing the horizontal distance between the operator and the work requires greater arm extension. In unrestricted work the operator can often compensate by moving closer to the task or repositioning the body. A glovebox restricts this movement because the arms pass through fixed gloveports.
LANL research identifies the resulting reduction in usable shoulder and elbow movement as an important ergonomic consideration. As working distance increases, awkward upper-extremity postures can occur earlier and operator discomfort and fatigue may increase.
This is particularly important for tasks requiring precision or dexterity. The location of frequently used tools, components and controls should therefore be considered when establishing the internal layout of the glovebox.
Source: Los Alamos National Laboratory, LA-UR-20-22703.
The usable depth of a glovebox is related to human reach. Increasing enclosure depth may provide additional process space, but that space has limited value if the operator cannot comfortably reach the equipment positioned within it.
The U.S. Department of Energy Nuclear Air Cleaning Handbook notes that gloveboxes are often no deeper than approximately 26 in (660 mm), reflecting the distance most arms can reach. Where greater depth is necessary, access from both sides of the enclosure may be considered.
Source: U.S. Department of Energy, Nuclear Air Cleaning Handbook, DOE-HDBK-1169-2003, Chapter 7 – Glovebox Filtration.
The gloveport establishes the position from which the arm enters the enclosure. Its height, horizontal position and orientation therefore affect the posture of the shoulder, elbow and wrist.
A poorly positioned port can require the operator to raise or lower the shoulder, abduct the upper arm, extend the elbow or deviate the wrist before the task itself begins. The effect can become more significant when the task is repetitive, requires force or must be maintained for an extended period.
Gloveport position should therefore be considered together with:
The geometry immediately surrounding a gloveport can affect the range through which the operator's arm can move.
LANL's published discussion of glovebox shielding describes the use of bevelled gloveports in shielding arrangements to increase the available range of arm movement. The paper also describes hinged shielding arrangements that can be moved for appropriate maintenance activities.
The general ergonomic principle is useful beyond the particular LANL application: structures surrounding a gloveport should be assessed for their effect on the angular movement of the forearm and upper arm rather than only for the clear diameter of the opening.
Source: Los Alamos National Laboratory, LA-UR-20-22703.
A glovebox intended for a range of operators should not be designed solely around an average-sized person. The limiting operator can differ according to the design requirement.
Smaller operators may govern maximum comfortable reach, while larger operators may govern clearances and the space required around the arms and body. The design population should therefore be established before gloveport position and internal working distances are finalised.
Relevant anthropometric dimensions can include standing or seated elbow height, forearm length, upper-arm length, shoulder breadth and forward reach.
See Anthropometric Data and Human Body Dimensions .
The position of the task relative to the gloveport determines the combination of shoulder and elbow movement required to reach it.
LANL's published assessment notes that insufficient distance between the glovebox interface and the operator's elbow can severely restrict the available elbow arc. Conversely, placing work too far into the enclosure requires greater extension of the arm.
The objective is therefore not simply to maximise or minimise one dimension, but to provide sufficient movement while keeping important tasks within a comfortable working region.
Source: Los Alamos National Laboratory, LA-UR-20-22703.
Reach should be considered together with task frequency. Frequently used items normally justify the most favourable positions, while less frequently used items may be positioned farther from the operator where this does not create an unacceptable handling or postural requirement.
The same principle applies to maintenance and abnormal tasks, but infrequent use should not automatically be taken as evidence that a difficult reach is acceptable. The required force, load, posture and consequences of losing control of an item must also be considered.
An operator may adopt additional forward reach or an awkward posture simply to obtain a better view of the task. Reach and visibility should therefore be assessed together.
LANL's research into shielding and glovebox ergonomics identifies reduced visibility as another factor that can affect dexterity and task performance. A design that places the work within an acceptable arm reach but requires poor head, neck or trunk posture for viewing has not solved the complete human-factors problem.
Source: Los Alamos National Laboratory, LA-UR-20-22703.
For frequently performed glovebox work, the preferred approach is to arrange the workstation around the task and intended operator population rather than using the maximum physical reach of an operator as the design target.
Particular attention should be given to frequently handled components, precision operations, forceful tasks and operations requiring prolonged posture. Mock-ups, ergonomic assessment or digital human modelling can be valuable where glovebox geometry is being established or substantially modified.
Human factors should be applied using engineering judgement, considering the task, user population, frequency, duration and consequences, rather than treating every recommended value as an absolute design limit.
This page forms part of the RoyMech glovebox ergonomics series: