Omni Containment Systems has worked with several kitchen exhaust cleaners to help solve many rooftop cases with the right grease containment solution. In most of these cases, we act as a grease-scene investigator; we carefully examine the rooftop and collect evidence. The evidence we gather can include the amount of grease output, the grease damage, equipment currently used, and the condition of the rooftop and fan. We gather as much information as possible and often request photographs with relevant aspects of the scene. Then, we analyze this information to help come up with the best solution. In this month’s case study, we are going to have you join us on one of these rooftop grease containment scenes in the case of the splattered rooftop.

Inspection & Investigation

Upon immediate inspection of these rooftop scenes, you are going to see an extensive case of grease pooling, splatter, and an overall rooftop grease disaster. Warning: This month’s case study will show scenes that some restaurant owners, facility managers, and inspectors may find disturbing. Let’s begin the investigation.

grease containment

  1. Why is there black grease splattered all over the roof?

As you can see, there is extensive grease splatter and not solely surrounding the upblast fan. In fact, this upblast fan is expelling grease splatter almost five feet out, pushing grease down and out the cap. Essentially, it is behaving like a grease volcano. If no solution is provided, it will continue to erupt, causing grease splatters and grease pools.

grease containment 

  1. How did grease get into the gutter system?

Upon further investigation, grease has made its way to the grease gutter system, putting this restaurant in violation of EPA stormwater runoff regulations. The number one enemy of rooftop grease is water. While all rooftops do factor in water because it’s a natural occurrence, they do not factor in grease. Rooftop water runoff will carry the grease, as seen above, to the gutter system and onto the side of the building or walkway. This must be resolved quickly to avoid costly EPA violations and increase safety around the building.

rooftop grease containment

  1. Why does this fan have a “rain cover” on top of an upblast fan?

We have determined that the location of this rooftop may be in an area that is super rainy because of the amount of stormwater runoff. However, this cover is not to prevent rain from getting into the system. Although it looks like an umbrella, this cap is placed to prevent grease from becoming airborne and splattering more on the rooftop. Unfortunately, this solution backfired, and the cap is actually the culprit behind the splatters rather than preventing it.

grease containment

  1. Why did this grease containment system fail?

Now that we have carefully analyzed the grease splatter around the fan, we still need to investigate the upblast exhaust fan. Upon immediate analysis, we find that this fan is breaking several NFPA 96 codes by not having a compliant hinge or grease catch. The NFPA 96 states, “ Rooftop termination shall be arranged with or provided with the following: (4) The ability to drain grease out of any traps or low points formed in the fan or duct near the termination of the system into a collection container that is noncombustible, closed, rainproof, and structurally sound for the service to which it is applied and that will not sustain combustion.” The above fan does not have a closed, rainproof, or structurally sound design.

The NFPA 96 also states, “ Rooftop termination shall be arranged with or provided with the following: (8) A hinged upblast fan supplied with flexible weatherproof electrical cable and service hold-open retainer to permit inspection and cleaning that is listed for commercial cooking equipment.” The fan above doesn’t have any hinge whatsoever. Hinges should cover at least 60% of the fan base to be considered safe for service personnel. These fans weigh anywhere from 80 – 400 lbs, so if they were to crash down on someone while they were cleaning, it could be deadly.

Solve the Case

With the amount of grease splatter on the rooftop, it’s difficult to tell just how much grease output this location experiences. However, due to the cap’s presence, grease is splattering all over the rooftop, which may also indicate that the kitchen exhaust ducts are not clean. This is extremely dangerous, and the restaurant is not in compliance with NFPA 96 standards. A common question is how often should my ducts be cleaned or inspected and by who? The frequency of inspecting your exhaust system depends on your cooking operations volume of cooking. Higher cooking volume means higher grease buildup and more frequent duct cleanings and inspections.

Refer to the NFPA 96 Table 11.3 below:

Second, this fan could be equipped with either our Grease Box, Grease Gutter Sidekick, High-Capacity Grease Gutter, or Roof Guardian. The Grease Box is perfect for commercial kitchens that need a little extra support. It has three tiers of our hydrophobic filters and is in a closed receptacle, so it is also wind and weatherproof. The Grease Gutter Sidekick is the perfect solution for normal commercial kitchens with average output, again utilizing our hydrophobic filters. The High-Capacity Grease Gutter surrounds the fan 360 degrees around the base, making it perfect for capturing higher amounts of grease output. Finally, the Roof Guardian, when sized correctly, can aide this fan in catching the grease splatter around the fan due to the cap.

Third, this fan needs a hinge. Our patented Super Hinge is the only NFPA 96 compliant hinge on the market. As you can see in the pictures above, the cap above the fan is tilted. This is due to taking the fan off to clean and setting the fan down on its side during the cleaning. Continuing to do this will eventually force the cap to snap off the top of the fan. We offer different sizes to provide fans of varying lengths the proper amount of coverage. As stated earlier, hinges should span across at least 60% of the fan base to be considered safe enough for service personnel to clean. This is not an NFPA 96 requirement; the 60% is what Omni Containment Systems has found to be the best and safest length.


Congratulations! You are officially a grease-scene investigator. Now that you have joined us on this case, become your own rooftop grease detective. Many of these types of cases can be avoided by recognizing potential problems before they start. You can stop problems before they start by using your investigative skills and remaining proactive. Contact us today to learn how we can help get your rooftop maintained and protected from fires in your commercial kitchen!