Paint shop: emissions, VOC, operating rules, measurement and operating permit

Paint shop: emissions, VOC, operating rules, measurement and operating permit

From an air-protection perspective, a paint shop is often a significant stationary pollution source. It is not only about spraying paint. The assessment usually covers the whole technological unit: preparation of coating materials, application, ventilation, flash-off, drying, curing, equipment cleaning, filtration, exhausts, consumption of organic solvents and maintenance of operating records.

In practice, paint shops most often involve emissions of volatile organic compounds (VOC), sometimes also particulate pollutants from overspray, odour load, exhaust requirements, emission measurement and correct setting of the operating permit. For larger or technically more complex paint shops, an operating rule and regular solvent consumption balance are also important.

For a paint shop it is not enough to know that "painting takes place there". For a proper assessment, what matters is how much organic solvent is consumed by design and in reality, what technology is used, where waste gases are discharged and how emissions are limited.

VOC and organic solvents

VOC stands for volatile organic compounds. In paint shops, VOC are usually released from coating materials, thinners, hardeners, cleaning agents, degreasers and other products containing organic solvents.

An organic solvent is a substance used, for example, to dissolve, dilute, adjust viscosity, clean, degrease or modify surface tension. In paint shops, solvents therefore appear not only in the paint itself, but also in auxiliary operations.

Typical VOC sources in a paint shop:

• solvent-borne coating materials,
• thinners,
• hardeners,
• cleaning agents,
• degreasing products,
• washing of spray guns and coating equipment,
• open containers and handling of products,
• flash-off after coating application,
• drying or curing.

For permitting and record-keeping, it is important to distinguish whether the issue is actual consumption of coating materials or consumption of organic solvents. Solvent consumption often determines source classification, operator obligations and whether the installation is a listed stationary source.

When a paint shop is a listed source

For paint shops, total projected consumption of organic solvents is decisive. Depending on the activity, this may involve application of coating materials, coating of wooden surfaces, vehicle refinishing, coating in vehicle production or related degreasing and surface cleaning.

In simplified terms, for ordinary application of coating materials a significant threshold is often total projected consumption of organic solvents of 0.6 t/year or more. For vehicle refinishing in repair shops, the relevant threshold is 0.5 t/year or more. Exact classification always depends on the specific activity and the applicable source code.

Practically important: a source cannot be classified from the name "paint shop" alone. It is necessary to know the technology, type of coating materials, solvent consumption, designed capacity and related operations.

Emissions from a paint shop are not only stack concentration

When assessing a paint shop, concentration of organic substances in the exhaust is often measured, usually as TOC — total organic carbon. That is important for verifying the emission limit. At the same time, it may not be the only figure the operator needs.

For paint shops, three different perspectives are usually used:

1. pollutant concentration in the exhaust,
2. mass flow of emissions,
3. annual balance of VOC inputs, outputs and emissions.

Exhaust concentration shows how much pollutant is in the discharged air. Mass flow states how much substance leaves per unit of time. The annual balance shows the overall impact of operation over a year.

In a paint shop with high air flow, even a seemingly low concentration can be associated with a significant mass flow. Conversely, a small exhaust with higher concentration may not have the same annual significance as a large extraction system.

Paint shop exhausts

Exhausts are key for a paint shop. They remove air from the spray booth, dryer, curing oven, mixing room, preparation area, gun cleaning station or other parts of the technology. For emission assessment it is necessary to know which exhausts belong to which parts of the operation and whether they are truly representative for discharge of pollutants.

For exhausts, the following are assessed in particular:

• number and location of exhausts,
• connection to specific technological parts,
• waste air flow rate,
• temperature and humidity of waste gas,
• accessibility of measurement locations,
• existence of measurement ports,
• uniformity of flow in the measurement profile,
• connection to filtration or separation equipment,
• operating regime during measurement.

A common problem in paint shops is that the technology may have several exhausts of different significance. Extraction from the application area has a different character from extraction from drying and from curing. If an emission limit applies to all exhausts from individual spaces, measurement and records must be designed to meet that requirement in practice.

Filtration and emission reduction

Filtration in paint shops serves several functions. It captures overspray, protects fans and ductwork, reduces particulate emissions and may be part of the overall emission control system. For organic solvents, however, ordinary mechanical filtration alone usually does not mean VOC removal.

It is therefore necessary to distinguish what the equipment actually captures:

A common mistake in paint shops is assuming that "filters are there, so emissions are solved". For particulates that may be partly true, but for VOC it is necessary to verify whether the technology actually captures or destroys organic substances. If it is only an overspray filter, VOC usually pass on into the exhaust.

VOC balance

VOC balance is one of the most important tools for assessing a paint shop. It is not merely an accounting overview of paint consumption. A proper balance must work with the content of organic solvents in input raw materials and with what happens to those solvents in operation.

The balance usually includes:

• coating materials,
• paints,
• thinners,
• hardeners,
• cleaning and degreasing agents,
• solvents used for equipment washing,
• waste solvents,
• residues of coating materials,
• waste handed over to an authorised person,
• possibly regenerated or reused solvents.

The purpose of the balance is to determine how much VOC entered the operation and what share was emitted to air, captured, destroyed, removed as waste or otherwise used. For some sources, the balance may also serve as a method of determining emission levels by calculation.

Simple balance principle

VOC input
- VOC in waste
- VOC captured or destroyed
- VOC in product
= estimated VOC emissions

This principle is simplified. In a specific paint shop the procedure must be adapted to the technology, type of products used, records kept and requirements of the operating permit.

Operating records

Operating records are for a paint shop practically as important as emission measurement itself. If the operator does not keep adequate records of consumption, operating hours, filter changes, waste and technology regime, it is often difficult to demonstrate the actual state of operation during an inspection or when preparing summary operating records.

Depending on the nature of the operation, paint shop operating records should track in particular:

1. consumption of coating materials,
2. consumption of thinners, hardeners and cleaning agents,
3. VOC content in products used,
4. paint shop operating hours,
5. operating regimes of individual parts of the technology,
6. filter replacement and maintenance,
7. function of extraction and filtration equipment,
8. quantities of waste solvents and paint residues,
9. emission measurement results,
10. fulfilment of operating permit conditions.

Operating records are not a formality. They are the main basis from which it is demonstrated retrospectively how the source was operated and whether it complied with permitted parameters.

Without ongoing records it may be difficult to demonstrate that the paint shop did not exceed projected consumption of organic solvents or that it fulfils operating permit conditions.

Emission measurement from a paint shop

Emission measurement at paint shops is carried out under operation that should correspond to normal or emission-representative regime. It is not enough to measure on a day when little painting takes place, different products than usual are used, or a part of the technology significant for emissions is not in operation.

Measurement at paint shops often focuses in particular on:

• TOC as an indicator of total organic substances,
• possibly specific organic substances according to the permit or technology,
• particulate pollutants where relevant,
• volumetric flow of waste air,
• gas temperature, pressure and humidity,
• technology operating parameters during measurement,
• filtration or separation efficiency where that is the purpose of measurement.

It is important that the measurement location on the exhaust allows representative sampling. If the exhaust does not have a suitable measurement profile, sufficient straight sections, access, working platform or measurement ports, measurement may be technically complicated and the result harder to defend.

What must be clear before measurement

Before measurement the following should be determined:

• which exhaust is measured,
• which part of the technology is connected to the exhaust,
• which coating material is used,
• what the application regime is,
• whether drying or curing is taking place,
• what the extraction output is,
• whether filtration is in normal operating condition,
• whether operation corresponds to the operating permit.

For paint shops it is advisable to link emission measurement with review of operating records. The measured exhaust concentration alone is important, but without knowledge of solvent consumption and operating regime it may not provide a complete picture.

Paint shop operating rule

An operating rule is a document describing how the source is to be operated so that air-protection conditions are met. For sources where an operating rule is required, it is part of the operating permit. The operating rule should not be a generic document copied from equipment catalogues, but a practical guide for the specific paint shop.

For a paint shop, the operating rule should typically address:

• description of the technology and individual operating parts,
• coating materials and organic solvents used,
• exhausts and extraction from individual parts of the technology,
• filtration and separation equipment,
• operating parameters monitored by operators,
• normal operating conditions,
• start-up and shutdown procedures,
• operating measures in case of extraction or filtration failure,
• maintenance of operating records,
• filter maintenance and replacement,
• emergency and extraordinary situations,
• method of checking fulfilment of emission conditions.

A quality operating rule should be usable for operators, the operator and the inspection authority. It should clearly state how the technology is to be operated, what is monitored, what is recorded and how to proceed in case of deviation from normal state.

Operating permit

The regional authority issues an operating permit for listed stationary sources. For paint shops it is necessary first to determine correctly whether the technology falls under Annex No. 2 to the Air Protection Act and under which code. Further requirements follow from that, such as expert opinion, operating rule, emission limits, emission measurement or operating records.

An operating permit usually sets:

• source classification,
• permitted capacity or consumption of organic solvents,
• emission limits,
• technical operating conditions,
• requirements for emission measurement,
• requirements for operating records,
• operating conditions for filtration or separation,
• obligations in case of faults and extraordinary situations,
• possibly requirements for an operating rule.

For a new paint shop, technology change, increase in solvent consumption, replacement of spray booth, exhaust change or change of filtration technology it may be necessary to obtain a new permit or amend the existing operating permit. It always depends on whether parameters relevant to air protection are changing.

When measurement alone is not enough and documentation is needed

Sometimes the operator orders only emission measurement, but the real problem is broader. Measurement may show whether an emission limit is met, but by itself it does not resolve incorrect source classification, missing operating permit, incomplete VOC balance or an outdated operating rule.

Typical situations where documentation must be addressed more comprehensively:

• the paint shop has reached or exceeded the threshold for consumption of organic solvents,
• the operator is changing coating materials or technology,
• a new spray booth or dryer has been added,
• exhausts or filtration equipment are changing,
• the regional authority or Czech Environmental Inspectorate requests supplementary documentation,
• operating records do not correspond to actual operation,
• an old permit does not correspond to current technology,
• it is unclear whether the source is correctly classified,
• the operator has no VOC balance prepared.

In such cases it is advisable first to carry out a technical and legislative review of operation. Only then is it proposed whether emission measurement, operating permit amendment, operating rule update, expert opinion or supplementation of operating records is needed.

Most common mistakes at paint shops

In practice, paint shops repeatedly show mistakes in records, source classification and interpretation of what is actually an organic solvent. The link between actual operation, operating permit and emission measurement is also often missing.

Common mistakes:

• consumption is recorded in kilograms of paint, but not in quantities of organic solvents,
• VOC in cleaning and degreasing agents are not addressed,
• exhausts are not clearly assigned to technology,
• overspray filtration is mistaken for VOC removal,
• measurement is carried out under non-representative operation,
• operating records do not include filter changes and operating hours,
• VOC balance is not prepared or does not correspond to reality,
• the operating rule is generic and does not match the specific paint shop,
• the operating permit does not correspond to current technology,
• change of coating materials or capacity is not reflected in documentation.

Auxiliary operations are especially risky to underestimate. Washing spray guns, cleaning containers, degreasing surfaces or handling paint residues can be significant for VOC even when it is not painting itself.

How to proceed for a new or modified paint shop

For a new paint shop or change to existing technology it is advisable to proceed systematically. First, source classification and projected consumption of organic solvents should be verified. Then exhausts, filtration, emission limits, measurement, operating records and documentation for the regional authority are assessed.

Recommended procedure:

1. describe paint shop technology,
2. identify coating materials, thinners, hardeners and cleaning agents used,
3. determine projected and expected actual consumption of organic solvents,
4. determine source classification under Annex No. 2 to the Air Protection Act,
5. check exhausts and measurement locations,
6. assess filtration and measures to reduce emissions,
7. design operating records and VOC balance,
8. verify need for operating rule, expert opinion and operating permit,
9. set requirements for emission measurement,
10. prepare documentation for the regional authority.

This procedure reduces the risk that the paint shop is technically completed but problems subsequently arise with the permit, exhausts, measurement locations or records.

Summary

From an air-protection perspective, a paint shop is a typical VOC emission source. What matters is not only painting itself, but the whole operating unit: consumption of organic solvents, coating materials, cleaning, degreasing, filtration, exhausts, emission measurement, VOC balance, operating records and operating permit.

Ordinary overspray filtration does not automatically mean VOC removal. Likewise, one-off emission measurement alone does not replace correct source classification, operating rule or ongoing records of solvent consumption. For paint shops it is therefore advisable to combine technical assessment of the technology with the legal and record-keeping framework of air protection.

Send us a description of the paint shop, a list of coating materials and thinners used, safety data sheets, an exhaust schematic, projected consumption of organic solvents or the existing operating permit. We will propose a suitable procedure for emission measurement, VOC balance, operating rule, operating records or paint shop operating permit.

Factual basis of the article

The article is based mainly on the following regulations:

• Act No. 201/2012 Coll., on air protection,
• Decree No. 415/2012 Coll., on permissible pollution levels and their determination.

Act No. 201/2012 Coll. defines, among other things, volatile organic compound, organic solvent, stationary source, emission, emission limit and obligations of the operator of a stationary source. Decree No. 415/2012 Coll. sets requirements for sources using organic solvents, including application of coating materials, emission limits, technical operating conditions and requirements related to VOC.