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Stool and Chair Selection

Quick Tips #248
Introduction

When designing a work station, the chair is a very important consideration. The right chair provides the basis of support for the entire body. A well-designed and adjusted chair can improve circulation and posture and reduce fatigue and back strains.

Common Terms

Articulating seat allows the user to adjust the angle of the seat.
Back tilt allows the user to adjust the angle of the back support in relation to the seat.
Forward-sloping seat is when theback of the seat is higher than the front edge also called a waterfall front.
Lumbar support is the part of a chair backrest that supports the muscles of the lumbar region (lower back) when sitting upright.

Pneumatic height adjustment uses a pressurized cylinder to make height adjustments from a seated position.

Mechanical height adjustment requires the user to spin the chair to move a threaded rod up or down in the base, which changes the seat height.

Stool is a backless, armless seat; unfortunately, this definition does not hold true to manufacturers. The terms chair and stool are sometimes used interchangeably among manufacturers. Some manufacturers use height, the lack of a backrest, or presence of foot ring to designate the stool label.

Task Chair/Stool is designed for people whose job consists of one main task: looking into a microscope, talking on the phone, or using a video display terminal.

Vertical back adjustment is the ability to change the height of the back support.

Standards

California Technical Bulletin 117 (TB 117) is a minimum, mandatory standard for all upholstered furniture for sale in California. It contains both open flame tests and smoldering cigarette tests for the component materials that make up the upholstered furniture. TB 117 is enforced in California by the California Bureau of Home Furnishings and Thermal Insulation (the Bureau). The standard applies to all upholstered furniture offered for sale in the state of California, regardless of its geographical source (foreign or domestic).

The American National Standards Institute (ANSI) and The Business & Institutions Furniture Manufacturers Association (BIFMA) set minimum performance standards for chairs and stools. To ensure the durability of your chair/stool you should look for this compliance.

At a minimum, the following criteria should be considered when selecting a chair:

Is the chair seat height easily adjustable?

  • Most chairs have a pneumatic adjustment that allows the seat height to be adjusted while you are seated; others have a mechanical adjustment (spinning of the chair)
  • The seat should be adjusted so the back of the knee is approximately level with the hip

Is the range of the seat height adjustment acceptable for your needs?

  • The basic formula to determine the correct seat height is the work surface minus 10 inches
  • This number should be the mid-point of your adjustment range. For example:

     34" work surface
    -10"
    24" Mid-point of seat-height adjustment

  • Your chair should adjust at least 2-1/2" above and 2-1/2" below this mid-point
  • A chair with seat height range of 21-1/2"–26-1/2" would be ideal for a 34" work surface
  • If you have multiple work heights, choose a chair with a broader height adjustment

Is the backrest adjustable and/or does it recline?

  • The backrest should be at least 18 inches tall and 24 inches wide and should support the mid-back, upper-back and lumbar area
  • Some backrests are adjustable forward and backward in addition to vertical
  • The best backrests are not locked into one position; they recline and track with your back

Is the seat large enough?

  • The seat should be at least 1" wider than the thighs and hips on either side
  • Waterfall seat fronts and concave seat designs offer greater comfort and allow for even weight distribution

Does your application require armrests?

  • If so, the armrests should be cushioned and be easily adjusted from a seated position
  • Adjustability should include moving the armrests closer together and further apart in addition to height adjustments

What chair covering best fits your application?

  • Vinyl and vinyl-like coverings are easy to clean and resist spills, but the fabric may heat up and cause moisture build-up wherever the fabric contacts the skin
  • A cloth fabric is the most common covering but it is less resistant to spills and is more difficult to clean
  • Cloth, covered seat pans can also be a source of dust mite allergen

Does your application require casters?

  • Most chairs come standard with stationary glides
  • Casters can be purchased for carpet or hard floor applications
Commonly Asked Questions

QWhat type of casters do I need? ACarpet casters are generally made from hard plastic and have dual-wheels. Casters for hard floors have a single wheel and are usually made from hard rubber. QWhat is the weight limit on a chair? AIt varies by chair and manufacturer. As a general rule, most chairs have weight limits around 300 lbs.; some manufactures have chairs with capacities over 500 lbs. QWhat is the best posture to have while seated? ASome general guidelines are as follows:

  • Seated upright with ears, shoulders and hips in alignment
  • Arms close to the side of your body
  • Forearms approximately parallel to the floor
  • Wrists relatively straight (neutral position)
  • Thighs parallel to the floor and supported by the chair
  • Feet firmly on the floor or foot rest
  • Shoulders in a relaxed position
  • Lower back is properly supported
Source

ANSI/BIFMA Standard X5.1-1985

State of California, Department of Consumer Affairs Bureau of Home Furnishings and Thermal Insulation
North Highlands, California 95660

Cornell University Ergonomics Web Page

Bevco Precision Mfg Co

Biofit Engineered Products

(Rev. 1/2012)


Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at www.grainger.com/quicktips.

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Please Note:
The content in this newsletter is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific compliance questions should refer to the cited regulation or consult with an attorney.


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