A coating booth extracts paint mist generated during application to protect the working environment.

However, air extracted by the booth is not necessarily being treated safely.

Paint mist.
Dust.
Paint residues.
Fine particles that pass through filters.
Contamination adhering inside ducts.
Dried coating flakes.
Fine contaminants dispersed from wet booths.

If these leave the factory in the exhaust, they can cause problems outside.

For example, powder deposits on neighboring factory roofs or vehicles.
Exterior walls or windows become dirty.
Particles adhere to another company’s products.
Dust enters through air-conditioning intakes.
Complaints come from the industrial park or neighbors.

Booth-exhaust particulate emissions extend beyond the factory interior.
They affect external complaints, environmental management, customer audits, and company reputation.

Coating booths therefore require checking what is being released outside, as well as whether extraction is working.

1. Mist Extracted by the Booth Goes Somewhere

Paint mist generated during application is drawn into the booth exhaust.

The important point is that extracted mist does not disappear.

Dry booths capture it with filters.
Wet booths capture it with water.
Powder booths capture it with recovery equipment or filters.

However, inadequate collection may allow some mist or dust to leave with the exhaust.

A coating booth therefore does more than extract mist.
Reliable collection after extraction, preventing release outside, is important.

2. Emitted Particles Can Be Difficult to See

Exhaust particles are not always visibly emitted in large quantities.

White smoke or colored mist may be clearly visible from outside.
However, fine particles can be difficult to see.

Even when hard to see, they gradually deposit around the site.

Around exhaust outlets.
On building roofs.
Near duct outlets.
On neighboring factory walls.
On parked vehicles.
At air-conditioning intakes.
On goods stored outdoors.

Gradual deposits may eventually prompt external reports of dirt, drifting powder, or paint-like material adhering to surfaces.

External complaints can seem sudden.
In reality, small emissions may have accumulated over a long period.

3. Particulate Complaints Readily Become Management Issues

Internal coating defects can be investigated and improved within the company.

However, particulate emissions leaving the factory affect more than internal operations.

Neighboring factories.
Industrial-park management.
Customers.
Authorities.
Local residents.
The parent company.

The impact can extend to many stakeholders.

Deposits on another company’s products or equipment in particular may lead to compensation or trust issues.

External complaints are more than equipment problems.
They are risks to factory operations.

Booth-exhaust particulate emissions therefore deserve attention from factory managers and company management, as well as shop-floor supervisors.

4. Poor Filter Control Leads to Particulate Emissions

Filters are extremely important in dry booths.

They capture paint mist and particles.
However, improper filter control can allow particles to escape outside.

Examples include the following conditions.

• Excessively clogged filters
• Torn filters
• Gaps around installed filters
• No defined filter replacement interval
• Inexpensive filters with insufficient collection performance
• Operation with some filters removed by operators
• No differential-pressure control

Clogging reduces airflow.
Tears or gaps allow mist and particles to pass through.

Filters therefore need to be checked for proper functioning, rather than simply whether they are installed.

5. Wet Booths Do Not Eliminate All Particles

Wet booths capture paint mist with water.
They may therefore reduce particles or mist more readily than dry booths.

However, wet booths do not completely eliminate particles or mist.

The following conditions make contamination more likely to enter the exhaust.

• Insufficient water volume
• Uneven water flow
• Accumulated sludge
• Clogged water passages
• Unsuitable booth chemicals
• Excessive foaming
• Contaminated mist separators
• Paint residues on fans or ducts

Water and sludge management in wet booths also contributes to particulate-emission control.

Water-based collection should not automatically be assumed reliable.
Check that the water is properly managed.

6. Duct Contamination Can Become Re-Entrained

Paint mist, particles, oil, and tar constituents gradually adhere inside exhaust ducts.

Accumulated contamination increases exhaust resistance.
Dried paint residues or dust may also flake off and leave in the exhaust.

The following locations require particular attention.

• Duct bends
• Areas where air velocity decreases
• Exhaust-fan blades
• Ducts downstream of filters
• Areas near exhaust outlets
• Long ducts without inspection openings

Duct contamination is normally difficult to see.
It is therefore often left untreated until a problem becomes apparent.

Particulate-emission prevention requires checking duct and fan cleanliness as well as the booth itself.

7. Dirty Exhaust-Fan Blades Also Reduce Capacity

Paint residues or dust on exhaust-fan blades reduce fan capacity.

Blade imbalance can also cause vibration or abnormal noise.
Reduced airflow may weaken booth extraction.

Blade contamination causes the following problems.

• Reduced exhaust airflow
• Mist remaining in the booth
• Poor particle collection
• Noise and vibration
• Increased motor load
• Higher electricity costs
• Failure risk
• Re-entrainment of contamination into the exhaust

A rotating fan does not by itself demonstrate that conditions are acceptable.

Regularly check blade contamination, vibration, noise, and airflow.

8. Exhaust-Outlet Location Also Affects External Complaints

Whether particulate emissions lead to external complaints also depends on exhaust-outlet location.

Even with the same emission quantity, outlet direction and height change the area affected.

For example, the following situations require attention.

• The outlet points toward a neighboring factory
• The outlet is positioned low
• An air-conditioning intake is nearby
• A parking area is nearby
• Outdoor storage goods are nearby
• Wind carries particles in a particular direction
• Exhaust strikes a building wall and returns

Particles leaving the outlet follow outdoor airflow.
Exhaust-system design therefore requires checking outlet direction, height, and surroundings.

9. Particulate Control Is Particularly Important in Powder Coating

Powder coating is advantageous for reducing VOCs.
However, particulate control is extremely important.

Because the coating material is a powder, inadequate booth extraction or recovery may allow it to escape outside.

Check the following items in powder coating.

• Powder-booth extraction condition
• Recovery-equipment performance
• Filter clogging
• Powder leakage
• Color-change cleaning
• Reclaimed-powder control
• Operators’ dust exposure
• Particulate emissions from exhaust outlets

Low VOCs do not mean that powder coating has no environmental impact.
Proper particulate controls are necessary.

10. Low Transfer Efficiency Also Increases Exhaust Particles

Transfer efficiency is the proportion of sprayed paint actually deposited on the workpiece.

Low transfer efficiency increases the amount not deposited.
Some becomes booth mist, filter load, sludge, or exhaust particles.

Particulate-emission controls must therefore extend beyond the exhaust side.

How much paint is being sprayed wastefully?
Are gun conditions appropriate?
Is air pressure too high?
Is gun distance excessive?
Do poor fixture or workpiece arrangements allow paint to escape?
Does poor electrostatic grounding reduce transfer efficiency?

These points also need checking.

Reducing overspray at its source is important for reducing particles.

11. Check the Exhaust Outlet to Prevent External Complaints

Particles may be released outside even when the booth interior appears normal.

Checks at the exhaust outlet are therefore necessary.

Check the following items.

• Are particles deposited around the outlet?
• Are building exterior walls dirty?
• Is colored mist visible from the outlet?
• Are deposits present on nearby roofs or vehicles?
• Does wind carry particles?
• Are odors strong near the outlet?
• Do conditions change after cleaning exhaust filters or ducts?

Preventing external complaints requires viewing the company’s equipment from outside the factory, as well as within it.

This protects company reputation as well as supporting environmental management.

12. Common Particulate-Emission Control Issues in Factories in Vietnam

The following particulate-emission issues commonly arise in factories in Vietnam.

Assuming conditions are acceptable if booth extraction works.
Not regularly checking exhaust outlets.
Having no filter replacement criteria.
Not checking incorrect filter installation.
Not cleaning ducts.
Not checking fan-blade contamination.
Inadequate reclaimed-powder control in powder coating.
Ignoring the site’s relationship to neighboring factories.
Not checking wind direction or outlet height.
Responding only after external complaints occur.

Exhaust particles can be hard to see from inside the factory.
A system for regular external checks is therefore necessary.

13. Items to Check for Booth-Exhaust Particulate Control

The following checks provide a practical way to manage booth-exhaust particles.

1. Booth Interior

Check retained mist, booth contamination, and airflow at the working position.

2. Filters

Check clogging, tears, installation gaps, and replacement intervals.

3. Wet-Booth Water

Check water volume, flow, sludge, foaming, and chemical effectiveness.

4. Ducts

Check contamination, clogging, bends, inspection openings, and cleaning history.

5. Exhaust Fan

Check blade contamination, vibration, abnormal noise, and reduced airflow.

6. Exhaust Outlet

Check particle deposits, exhaust direction, height, and surroundings.

7. External Environment

Check positions relative to neighboring factories, parking areas, air-conditioning intakes, and outdoor storage goods.

8. Transfer Efficiency

Check overspray quantity, paint losses, gun conditions, and fixture arrangement.

9. Powder Coating

Check powder leakage, recovery equipment, filters, and color-change cleaning.

10. Records

Retain external inspection results, cleaning history, filter replacement history, and complaint history.

14. The Value CoatureVietnam Sees in Particulate-Emission Control

CoatureVietnam regards booth-exhaust particulate control as more than environmental management alone.

Particulate-emission control is quality control.
It protects neighboring sites.
It improves working conditions.
It reduces paint losses.
It protects company reputation.

Examining what leaves the booth reveals the condition of the coating process.

High mist levels may indicate poor transfer efficiency.
Filters that clog readily may indicate high paint losses.
Dirty ducts may indicate inadequate maintenance management.
Particles released outside create environmental risk.

CoatureVietnam examines booth exhaust from the following perspectives.

• Reduce mist at the source
• Capture it reliably in the booth
• Manage filters and water
• Clean ducts and fans
• Check external effects at the outlet
• Improve transfer efficiency and reduce paint losses

This puts CoatureVietnam’s guiding principle,
“Coating the Future with Science and Care”,
into practice.

Science means checking particle sources, collection conditions, exhaust routes, and external effects.
Care means creating a coating shop that does not burden operators, neighboring factories, or the local environment.

Conclusion

Mist extracted by a coating booth flows somewhere.
If not captured by filters or water, some may leave with the exhaust.

Booth-exhaust particulate emissions extend beyond the factory interior.

Deposits on neighboring factory roofs or vehicles.
Entry through air-conditioning intakes.
Dirty exterior walls.
Deposits on other companies’ products.
Reports from industrial parks or customers.

These may lead to external complaints.

Coating booths therefore need checks on what is released outside, as well as whether extraction works.

Filters.
Wet-booth water.
Sludge.
Ducts.
Fans.
Exhaust outlets.
Transfer efficiency.
Powder recovery.

Managing these together reduces external particulate emissions.

CoatureVietnam treats booth-exhaust particulate control as an important issue connecting environmental management, quality control, paint-loss reduction, and protection of neighbors, and provides improvement proposals suited to factories in Vietnam.