Why Smoke Isn’t Going Up Your Hood (Even at High Speed)

You turn your range hood to the highest setting...and the smoke still lingers. Sound familiar?

Many homeowners assume a high-CFM hood guarantees strong performance. But in reality, ventilation efficiency depends on much more than just fan power.

Let’s break down the real reasons why smoke isn’t being captured—and how to fix it.

1. Your Ductwork Is Restricting Airflow

This is the #1 reason for poor performance.

Even powerful hoods (900-1200 CFM) struggle when airflow is restricted by:

• Long duct runs (10+ feet)
• Multiple bends or elbows
• Angled or horizontal ducting

Each turn slows the air down. Each foot adds resistance.

Result: Smoke escapes instead of being pulled upward.

2. Too Many Turns (Especially 90°or 45°Elbows)

Every bend creates turbulence.

A single 90°elbow can significantly reduce airflow
Even 45°angles, when combined with long runs, impact performance

Imagine airflow hitting a wall and redirecting, it loses strength during the process.

3. Duct Size Is Too Small

If your duct diameter doesn’t match your hood, airflow gets choked.

High-CFM hoods typically require 8” ducting (or larger)
Smaller ducts = higher resistance

It’s like trying to push a lot of air through a narrow pipe.

4. Poor Hood Placement or Height

Even a perfect system won’t work if placement is off.

Too high above the cooktop = smoke escapes
Too low = inefficient capture area

✔ Ideal range: 30”–36” above the cooktop

5. External Vent Restrictions

Sometimes the issue is outside your home.

Common problems:

• Bird screens
• Roof caps with flaps stuck closed
• Debris buildup

Even partial blockage reduces airflow dramatically.

6. Negative Air Pressure (Make-Up Air Issue)

If your home is tightly sealed, the hood can’t pull air properly.

Signs:

• Opening a window improves suction
• Weak airflow even at max speed

The hood needs incoming air to replace what it’s exhausting.

7. It’s Not the Hood—It’s the System

A quick test:

1. Remove filters
2. Hold a tissue near the fan

If suction only works very close to the motor → airflow is restricted

This confirms the issue is in the duct system, not the hood

How to Fix It

To improve performance:

• Shorten duct length if possible
• Reduce number of bends
• Use smoother, wider angles
• Upgrade to proper duct size
• Check exterior vent cap
• Improve make-up air flow

Even small adjustments can make a big difference.