When we saw this story about commonly overlooked code requirements in the HVAC industry, we felt we had a responsibility to pass it along to our friends in the Hydronic Systems family because safety is our number one priority.

The article covers safety codes that are often overlooked according to the author and includes topics such as safety guardrails, insulating hot surfaces and sidewall grille spacing codes. It was originally published in the December 2014 edition of the ASHRAE Journal.


By Stephen W Duda, P.E., BEAP, HBDP, HFDP, Fellow ASHRAE Member, December 2014

In an Engineer’s Notebook column about a year ago,1 I gave an outline of several energy-reduction strategies sometimes overlooked in mechanical design. This month, I intend to point out some important safety-oriented code requirements that tend to be similarly overlooked in mechanical design. These are critical safety- or service-related features applicable to building mechanical systems—code requirements that are frequently overlooked by engineers, design-build specialists, contractors, and even code officials. These are all real examples from actual facilities upon which I have performed property condition assessments, peer reviews of other designs, or remodeling projects in which a different engineer was responsible for the original design.

Safety Guardrails Near Roof Edge

In my own experience, this may be the single most commonly and egregiously overlooked code requirement in HVAC practice, in consideration of how potentially catastrophic its omission may be. The 2012 International Mechanical Code2 Paragraph 304.11 requires guards to be provided where appliances, equipment, fans or other components that require service are located within 10 ft (3 m) of a roof edge or open side of a walking surface and such edge or open side is located more than 30 in. (762 mm) above the floor, roof or grade below. That clause goes on to say the guard needs to extend at least 30 in. (762 mm) beyond each end of the item of equipment, and the guard must be  at least 42 in. (1.07 m) tall designed not to pass a 21 in (533 mm) sphere (for example, a 42 in. (1.07 m) two- pipe handrail). Specific requirements for the loading withstand rating of the guard rail are given in the International Building Code.

The reason for this requirement is obviously one of safety for the mechanic who may be required to change a fan belt, replace filters, and perform routine service or major repairs. Imagine a worker tugging on a broken fan belt or a filter stuck in its housing that suddenly breaks free, sending the worker stumbling backward. Even a simple accidental slip or fall, especially when the roof is wet or icy, could be fatal. Although I quoted above from the 2012 IMC, the same clause has appeared in every edition since 2000 albeit with different paragraph numbering, and was even found in the now-obsolete BOCA Building Codes as far back as 1993. Yet as I drive  throughout my own hometown and on business travel throughout the Midwest, I observe many rooftop units and condensing units located very close to a roof edge  with no guard rail at all, or at most an insignificantly short parapet.