Gravity Vent vs. Smoke Vent?

Building inspectors says "gravity vents" have to be removed per code. I'm saying they're not gravity vents, they are smoke vents or post-fire smoke purge vents. They each have a flue damper inside with a chain to open/close them. This building is a metals recycling business with high risk of fire and smoke inside at times. I say installing a screened vent hood is a liability in this application.

What say you?

Roofguy- Just skimmed-over the post- I may be missing something. May be a dumb question: Why is a roofer tasking-on HVAC liability? Even as a GC, I would defer to my HVAC engineer/designer, especially when bldg. depts. involved!

In most Texas cities we sell the job, roof the job, get a check, repeat. Most consider chopped glass and foam a "coating" and no permit application is required.

On this particular job in a more strict city, it slipped thru the cracks because I submitted the Scope and Application for a recover with foam, but the inspector rejected and required a tear off. The city simply asked me to send letter saying: Inspector required total tear off.

They asked for no other details.

The entire issue revolved around the inspector being an idiot who knows next to nothing about commercial roofing. he's the clown who bounced on the roof and d "Feel those reverberations (steel deck), that means there is too much weight and the roof has to come off." He is a major league moron.

Good ending to a potential problem. I'll say you appear to be tenacious when challenged. Why didn't this come up before installation? Components are a major factor in a commercial roofing system. When permitting a large or small job here in Florida Where The Sun Shines a Damn Near Every Day the permit application goes through examination for components that meet SSBC codes. Do the authorities in Texas just willy nilly say" OK " and later decide after install that XYZ is wrong etc. Hmm Something fishy about that.

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I met the inspector and his boss in their office today. I prevailed on both of their objections. I brought a letter from the VP at JoSam, addressed to the inspector personally, stating that I was right about the drain domes.

Also brought proof that the vents are considered smoke purge vents not gravity vents. They agreed and retracted both objections

Good day.

Yes, that is the only provision I was able to find, but the question is: who gets to determine if it is considered a post-fire smoke purge vent or not? Secondly, I can see nothing that says that it would need to have screens installed as would a gravity vent per local code.

More importantly, I can see how adding screen to the hood of a smoke purge vent (to keep rodent/pigeons out) could be a liability as rising ash, paper could clog it up during a fire.

What is the difference between the two? They either are or are not per code or is it syntax we are dealing with? Understanding the code might help...

SECTION 912 POSTFIRE SMOKE PURGE SYSTEMS

912.1 Scope and purpose. The purpose of this section is to establish minimum requirements for the design and installation of postfire smoke purge systems, which are intended for the timely restoration of operations and overhaul activities once a fire is extinguished. Postfire smoke purge systems are not intended or designed as life safety systems and are not required to meet the provisions of Section 909. Postfire smoke purge systems shall be required in:

1. High-rise buildings subject to Section 403. 2. Buildings with any story exceeding 50,000 square feet (4645 m2) in floor area. 3. Building with spaces exceeding 100 feet (30 480 mm) from natural ventilation openings. Natural ventilation openings shall consist of operable windows and doors of at least 5 percent of the floor area or roof vents per Section 910. 4. High-piled stock or rack storage in accordance with the New York City Fire Code.

Exceptions: A postfire smoke purge system is not required in R-2 occupancies where either of the following conditions exists: 1. Openable windows. A postfire smoke purge system is not required where every habitable room located in dwelling units is provided with windows complying with Chapter 12 and all of the following: 1.1. Minimum window area. Each required window shall provide at least 12 square feet (1.1 m2) of glazed area. The total area of all such windows shall not be less than 10 percent of the floor area of the room or space served. 1.2. Minimum openable area. Each required window shall provide a minimum of 6 square feet (0.56 m2) of openable area. The total area of all such openings shall not be less than 5 percent of the floor area of the room or space served. In addition, each required openable area shall be: 1.2.1. Located wholly at least 30 inches (762 mm) above the finished floor; and 1.2.2. Fully openable to the minimum 6 square feet (0.56 m2), at all times and without limiting stops or devices. Such openings may be achieved through the use of double-hung, sliding, or similar types of windows. However, in the event of the use of casement-, hopper-, pivot-, or awning-type windows, such windows shall satisfy the requirements of this section only when they open to at least 75 degrees (1.22 rad)‡. 2. Smokeproof enclosures. A postfire smoke purge system is not required where all exits are constructed as smokeproof enclosures in accordance with Section 1019.1.8. 912.2 Postfire smoke purge systems in occupancy groups other than R-2.

912.2.1 General design requirements. Postfire smoke purge systems are permitted to use dedicated equipment, the normal building HVAC system or other openings and shall have the capability to exhaust smoke from occupied spaces. Smoke removal may be by either mechanical or natural ventilation, but shall be capable of removing cold smoke. Smoke removed from a space must be discharged to a safe location outside the building and shall not be recirculated into the building in accordance with the New York City Mechanical Code. 912.2.2 Exhaust capability. The system shall have an air supply and smoke exhaust capability that will provide a minimum of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) [0.005083/(s · m2)], whichever is greater. The system need not exhaust from all areas at the same time, but is permitted to be zoned based on the largest fire area served. For the purpose of calculating system size, the height of a compartment shall be considered to run from slab to slab and include the volume above suspended ceilings. Provisions shall be made for sufficient make-up air. The provisions may include operable windows, doors, building leakage, or mechanical systems. In buildings having occupied floors located less than 75 feet (22 860 mm) above the lowest level of Fire Department vehicle access, breakable windows may be utilized. 912.2.3 Operation. The postfire smoke purge system shall be operated by manual controls that are part of the fire command center, in accordance with Section 911, or fire alarm panel when a fire command center is not required. Such control center or panel shall display a graphic indicating the portions of the building served by each postfire smoke purge system. When a system is zoned into areas of operation less than the entire building, each zone shall have an individual control. Fire Department manual controls of postfire smoke purge systems shall not override the manual or automatic operation of the smoke control system. Such Fire Department manual controls shall override the fire shutdown signal from the fire alarm system. 912.3 Postfire smoke purge systems in occupancy Group R-2. Postfire smoke purge systems in R-2 occupancies shall comply with either Section 912.3.1 or 912.3.2. Smoke removed must be discharged to a safe location outside the building and shall not be recirculated into the building in accordance with the New York City Mechanical Code.

912.3.1 Stair ventilation. The top of all enclosed exit stairs shall be provided with a reversible fan system capable of introducing fresh air or exhausting air at a rate of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) [0.00508 m3/(s·m2)], whichever is greater, based on the area of the largest floor. Such system shall be operated by manual controls that are part of the fire command center, as per Section 911, or fire alarm panel when a fire command center is not required. Such control center or panel shall display a graphic indicating the portions of the building served by each post-fire smoke purge system. The operation of such system shall be controlled by Fire Department personnel by manually opening stair doors at the appropriate story. 912.3.2 Corridor ventilation. The ducts and fans that provide fresh air supply to the public corridors in accordance with the New York City Mechanical Code shall be provided with reversible fans and duct sizes capable of introducing fresh air to or exhausting air from the corridor at a rate of 6 air changes per hour or 1 cubic foot per minute per square foot (cfm/ft2) [0.00508 m3/(s·m2)], whichever is greater, based on the area of the largest apartment plus the area of the public corridor. Such system shall be operated by manual controls that are part of the fire command center, as per Section 911, or fire alarm panel when a fire command center is not required. Each floor to be ventilated shall be by individual controls. Such control center or panel shall display a graphic indicating the portions of the building served by each postfire smoke purge system. 912.4 Maintenance. The building owner shall maintain postfire smoke exhaust systems in good operational condition. Records of testing shall be maintained on the premises for inspection by the department and Fire Department personnel.

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