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airflow Issue

Excessive Negative Pressure

Too much negative pressure stresses booth structure,

Emergency: (877) 489-3727Start Diagnosis

What You're Experiencing

The paint booth is operating with excessive negative pressure. Doors are difficult to open, seals are being sucked inward, and the booth structure may be...

Visual Signs:

  • Doors very difficult to open
  • Door seals and gaskets sucked inward
  • Panel walls flexing inward
  • Ceiling tiles lifting or shifting
  • Manometer showing higher than normal negative reading

Sound Signs:

  • Loud whistling at door gaps
  • Popping or crackling sounds from booth panels

Safety Risks — Read Before Proceeding

medium

Structural damage to booth

Action: Reduce exhaust rate or increase supply to relieve pressure stress on booth structure.

medium

Door seal failure leading to contamination

Action: Constant stress on door seals accelerates wear. Plan for seal inspection/replacement.

Immediate Steps to Take

  1. 1

    Check if makeup air unit is running

  2. 2

    Verify supply fan belt is intact and tensioned

  3. 3

    Check intake filter condition

  4. 4

    Compare supply and exhaust damper positions

  5. 5

    Temporarily reduce exhaust fan speed if possible

  6. 6

    Check manometer reading

Common Causes

Here are the most likely reasons you're experiencing this problem, ranked by how often we see them.

Makeup Air Unit Not Running

common

The supply/makeup air unit is completely off, leaving only the exhaust running and creating extreme negative pressure.

Makeup Air Unit Reduced Capacity

common

Supply air unit is running but not at full capacity due to belt slippage, filter loading, or fan issues.

Exhaust Damper Too Open

occasional

The exhaust damper has been adjusted too far open, pulling more air than the supply can provide.

Supply Damper Restricted

occasional

The intake/supply damper is not opening fully, restricting the makeup air entering the booth.

Intake Filter Severely Loaded

occasional

Ceiling or intake filters are so clogged they're restricting supply air entry despite the unit running.

Interactive Diagnostic Tool

Excessive Negative Pressure Diagnostic

Step 1 of 5

Is the makeup/supply air unit running?

If unsafe at any point: If booth panels are significantly deforming or structure appears damaged, stop operations and call WERCS.

When to Call WERCS

While some issues can be resolved with basic troubleshooting, these situations require professional service:

  • Makeup air unit won't start or stay running
  • You cannot balance the system with damper adjustments
  • Booth structure appears damaged
  • Door seals are repeatedly failing
  • System needs professional balancing service

Priority Service Available

(877) 489-3727

Expert technicians nationwide

Excessive Negative Pressure FAQ

Common questions about this issue

Most booths are designed for -0.03 to -0.05 inches of water column (WC). Readings significantly more negative than this indicate a supply/exhaust imbalance. Check your booth specifications or contact WERCS for design information.
Slight negative pressure is good—it prevents overspray escape. EXCESSIVE negative pressure stresses the booth structure, wears out seals faster, and indicates your supply air system isn't keeping up with exhaust.
Common causes include: makeup air unit failure/fault, supply belt breaking, intake filters loading up, or exhaust filter replacement (new filters have less resistance than loaded ones, so exhaust flow increases).

Have a question not answered here?

Call us at (877) 489-3727

Related Problems

Pressure ImbalanceMakeup Unit Problems

Can't Fix It? We Can.

WERCS expert technicians service paint booths and extraction systems nationwide. 24/7 emergency service available.

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