Many restaurants operate with kitchen exhaust systems that were installed decades ago. These systems were often built under older standards, with limited oversight, or modified multiple times as kitchens changed hands. While some of these older exhaust systems may appear to work adequately, their design can hide serious risks.
This article explains, in simple and easy language, why very old kitchen exhaust systems can be dangerous, how improper setups develop over time, what risks they create, and why “still working” does not mean “safe.” It is written for restaurant owners and managers, not technicians or inspectors.
Why Old Exhaust Systems Still Exist
Commercial kitchens change owners frequently, but exhaust systems often remain the same. Replacing or redesigning an exhaust system can seem expensive, so older setups are kept in place as long as they continue to function.
In many cases, these systems were installed before modern fire codes and safety standards were enforced consistently. Others were assembled using available parts rather than proper designs. Over time, repairs and modifications may have made the system even less compliant.
The result is an exhaust system that may move air but does not meet today’s safety expectations.
When “It Still Works” Becomes a False Sense of Security
One of the most common mistakes restaurant owners make is assuming that airflow equals safety. If smoke is being removed and the kitchen does not feel excessively hot, the system is assumed to be fine.
However, exhaust safety is not just about airflow. It is about where grease goes, how heat is handled, and how fire would behave if something went wrong.
Old systems often lack proper separation between components. They may allow grease to accumulate in places where it should never be present. These issues do not always affect daily operations, which is why they are so often overlooked.
An Example of an Improper Fan Setup
In some very old systems, the entire exhaust fan is installed inside the hood or duct instead of being mounted externally. While this setup may move air, it creates significant risks.
Fans are designed to be isolated from grease-heavy areas as much as possible. When the fan sits inside the exhaust system, it is constantly exposed to grease, heat, and moisture.
This exposure accelerates wear, increases grease buildup, and raises the risk of fire. It also makes cleaning more difficult and less effective.
Why Fan Placement Matters
Proper fan placement is critical to exhaust system safety. Fans mounted outside the duct are easier to service, easier to clean, and less exposed to grease.
When a fan is installed inside the duct or hood, grease accumulates directly on moving parts. Over time, this causes imbalance, vibration, and mechanical failure.
More importantly, grease-coated fan components become ignition points if flames reach the exhaust system. What might have been a contained flare-up can become a serious exhaust fire.
Table: Old Exhaust Design vs. Proper Design
| System Feature | Very Old / Improper Setup | Proper Modern Setup |
| Fan placement | Inside hood or duct | Mounted externally |
| Grease exposure | Constant | Minimized |
| Ease of cleaning | Difficult | Accessible |
| Fire risk | High | Reduced |
This table shows why older designs create unnecessary risk.
Why Improper Setups Are “Asking for Trouble”
Improper exhaust setups are not always immediately dangerous, which is why they remain in use. Problems develop slowly.
Grease builds up faster. Components wear out sooner. Cleaning becomes less effective. Small issues are harder to detect.
Eventually, something fails. That failure often happens during peak operation, when heat and grease production are highest.
When this happens in an improperly designed system, the consequences are far more severe.
Why These Systems Often Pass for Years
Many old exhaust systems avoid scrutiny simply because no one looks closely. If inspections focus only on visible cleanliness, deeper design flaws go unnoticed.
In addition, some systems were installed before current codes existed. While they may be grandfathered in, that does not mean they are safe. Grandfathered systems are still responsible for preventing grease fires.
Safety does not expire just because equipment is old.
Cleaning Challenges With Old Systems
Very old exhaust systems are often difficult to clean properly. Access doors may be missing or poorly placed. Fan components may not be designed to be opened.
As a result, cleaning crews may focus only on accessible areas, leaving grease behind in critical locations. Over time, this leads to severe hidden buildup.
In systems where the fan is inside the duct, cleaning without damaging components becomes even more challenging.
Fire Risk in Improperly Designed Exhaust Systems
When grease builds up inside an improperly designed exhaust system, fire risk increases dramatically.
If flames enter the hood, they can travel directly into grease-coated components. Because the fan is inside the duct, fire spreads rapidly through the system.
These fires are difficult to contain and often extend beyond the kitchen.
Why Age Alone Is Not the Only Issue
Not every old exhaust system is unsafe. Some older systems were well designed and properly maintained.
The real issue is design combined with neglect. Poor design increases risk. Poor maintenance magnifies it.
Understanding this helps owners make informed decisions about whether a system can continue operating safely.
When an Evaluation Is Necessary
If an exhaust system looks unusual, operates differently than modern systems, or has components installed inside the duct, it should be evaluated.
An evaluation does not always mean immediate replacement. In some cases, modifications can improve safety significantly.
The key is understanding the actual condition and design of the system.
The Cost of Waiting Too Long
Delaying evaluation of an old exhaust system can lead to sudden failures, emergency repairs, or forced shutdowns after inspections.
These outcomes are disruptive and expensive. Preventive evaluation allows owners to plan upgrades or corrections on their own timeline.
How Bryan Exhaust Helps With Older Systems
Bryan Exhaust works with restaurant owners to assess older exhaust systems and identify design issues that increase risk.
By explaining what is safe, what is outdated, and what needs attention, we help owners make informed decisions rather than reactive ones.
Final Thoughts
Very old kitchen exhaust systems often continue operating simply because they always have. That does not mean they are safe.
Improper setups—such as fans installed inside ducts—create unnecessary risk, even if the system appears to be working.
Understanding the limitations of older designs allows restaurant owners to take action before problems arise. Safety should never depend on luck or age alone.
