May 20, 2019

Mr. Anthony Green
Green Manufacturing Solutions
3000 Trailside Drive
Lexington, Kentucky 40511

Dear Mr. Green:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA), regarding the definition of confined space¹ at 29 CFR 1910.146, as it may apply to large product heating and aging furnaces. The background information and questions you provided in your inquiry are paraphrased below. OSHA’s responses follow your questions.

Background.
Product parts are heated in the furnaces using natural gas to temperatures ranging from 700 ºF to 2200 ºF to facilitate material processing. The furnace doors are actuated remotely from either the cab of a forklift or a control panel. Parts are loaded and unloaded from the furnaces using forklifts during production runs. The furnaces range in size from 8 feet x 8 feet x 8 feet to 18 feet x 18 feet x 18 feet. Furnace access is provided through large garage door type units on the front of the units that move upward on a track system. The floor (hearth) of the furnaces range from 22 to 29 inches above the floor of the building depending on the size of the unit.

Question 1: Do these types of furnaces meet the definition of a confined space? Ingress and egress only require stepping up from the building floor to the hearth of the furnace.

Response 1: The furnaces as described above do meet the definitons of a confined space, based on your letter. Stepping into furnaces that are 22 to 29 inches above the building floor, which would require more than one step (9.5 inches)² to climb up, may be considered restricted. Additionally, you stated that the furnaces’ doors are remotely actuated. Since the furnaces’ doors are actuated remotely, an employee within this space cannot walk out of the space without restriction. Thus, entry and egress are restricted according to the standard's definition of a confined space.

Question 2: Is there a threshold limit to the height of the furnace hearth above the ground that is allowed before the space would be considered “limited or restricted means for entry or exit”? For example, if the furnace is less than 30 inches above the ground, it would not be considered to have “limited or restricted means for entry or exit”. Conversely, if the furnace hearth is greater than 30 inches above ground level, it would be considered “limited or restricted means for entry or exit”.

Response 2: If some special means of access such as ladders, and temporary, movable, spiral, or articulated stairs are needed to enter the space, they may be considered a limited or restricted means of egress making the space confined under the standard. Therefore, as noted in our first response above, stepping into furnaces, which would require more than one step (9.5 inches) to climb up, may be considered limited or restricted means for entry or exit.

Question 3: Regardless of furnace hearth threshold height, would using a small access stool be acceptable for ingress and egress of the furnace? If used, would this then meet the definition “limited or restricted means for entry or exit”?

Response 3: Similar to the response to #2 above, the need to use an access stool would likely mean the space has a limited or restricted means for entry or exit.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA’s interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA’s website at http://www.osha.gov. If you have any further questions, please feel free to contact the Office of General Industry and Agricultural Enforcement at (202) 693-1850.

Sincerely,

Patrick J. Kapust, Acting Director
Directorate of Enforcement Programs

¹ In accordance with 29 CFR 1910.146, "Confined space" means a space that: (1) Is large enough and so configured that an employee can bodily enter and perform assigned work; and (2) Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry.); and (3) Is not designed for continuous employee occupancy.

² In accordance with 29 CFR 1910.25 (c)(3), Have a minimum tread depth of 9.5 inches (24 cm).