《Standard for Emission of Air Pollutants from the Printing Industry》GB 37827-2019: The 3 Real Compliance Boundaries for Printing Plants—Fugitive Emissions/Fence-Line Monitoring Points/VOCs Treatment Facilities: The Monitoring Point Printing Plants Most Often Get Wrong

Our plant is located in an industrial town in East China. The RTO environmental treatment facility was installed during a 2019 upgrade. The acceptance report showed that all stack outlet data met the standards, and fence-line monitoring did not trigger any alarms. We had always considered compliance fully resolved.

In 2024, the town conducted a comprehensive inspection. The environmental authority brought a third-party contractor to monitor 8 points along our property boundary. At the point outside the southern perimeter wall, the VOCs concentration exceeded the limit by 1.6 times.

Stack outlet compliance and fence-line exceedance can both be true without contradiction.

The First Boundary: Stack Outlets and Fugitive Emissions Are Governed by Two Entirely Different Sets of Rules

Under GB 37827-2019, “organized emissions” refer to pollutants discharged through stack outlets and other emission outlets. Sampling is conducted within the outlet, and concentration is calculated using the emission-specific method. This is the portion that the factory can control internally—including what treatment equipment is installed, which processes are used, and how the piping is configured.

“Fugitive emissions” refer to pollutants released directly into the atmosphere from the plant without passing through a stack outlet. Sampling points are located outside the property boundary, with points arranged on the upwind and downwind sides of the perimeter wall. The logic is entirely different: it evaluates the plant’s overall leakage volume, including gaps around workshop doors and windows, tank breathing, flange joints on waste-gas pipelines, and volatilization during loading and unloading.

Therefore, even if stack outlets comply, a fence-line exceedance still matters. The two are not measuring the same thing.

In our case, the issue involved a VOC storage tank on the south side of the workshop without breathing-valve control. The ink-mixing room had no local exhaust, and the exhaust air was discharged directly toward the property boundary. The RTO treats major airflow streams and cannot address these small, dispersed leaks.

The Second Boundary: Fence-Line Monitoring Point Locations Determine Whether the Data Are Useful

Fugitive-emission monitoring along a property boundary cannot be conducted by selecting an arbitrary point for a single test. Clear placement rules apply:

The reference point should be located upwind—outside the property boundary on the upwind side of the prevailing wind—to measure the ambient background. The monitoring point should be located downwind—outside the boundary on the downwind side—to measure the plant’s contribution. The difference between the two values represents the plant’s actual contribution to the surrounding area.

The problem is that many printing plants place the reference point on the east side and the monitoring point on the west side. However, the prevailing wind in the area is southeasterly in summer and northwesterly in winter.

In other words, for a significant part of the year, the reference and monitoring points do not align with the prevailing wind direction. Although the data appear compliant, they measure the concentration difference between the eastern and western sides of the plant rather than the plant’s contribution to nearby residential areas.

The point identified during our inspection was outside the southern perimeter wall. The prevailing wind was east-southeast at the time, so the data were valid. The point on the north side was actually upwind under the prevailing wind and produced very low readings. Had we tested only the northern point, we would not have detected the problem.

The Third Boundary: “Compliance” of Treatment Facilities Has Two Different Meanings

There are two entirely different meanings of VOCs treatment-facility compliance, which printing plants most often confuse.

First: treatment efficiency compliance. The ratio of the inlet waste-gas concentration to the outlet concentration must reach a specified value, such as above 90%. This is a performance indicator of the facility itself.

Second: emission-limit compliance. The measured stack outlet concentration must not exceed the applicable standard limit. This depends directly on the inlet concentration: the lower the concentration entering the treatment facility, the easier the same facility can meet the emission limit.

Many printing plants focus only on treatment efficiency. An efficiency of 92% meets the requirement and produces a clean report. However, if a customer increases its order for solvent-based coatings and the stack outlet concentration doubles, treatment efficiency remains at 92%, but the emission limit is exceeded.

In 2023, our plant accepted a batch of solvent-ink work, and total non-methane hydrocarbons at the stack outlet increased from 38 mg/m³ to 71 mg/m³. RTO treatment efficiency remained unchanged during those 2 months at approximately 93%, but the measured value had only 11 points of margin below the limit.

After that incident, we introduced an internal rule: issue an alert when stack outlet concentration reaches 75% of the limit and stop accepting solvent-based orders when it reaches 85%. This rule was not included in any official document, but it was more effective than any document.

Three Actions Printing Plants Can Take for Fence-Line Compliance

First, calculate the prevailing wind direction before prioritizing upgrades. We modified the VOC mixing room on the south side of the plant by adding local exhaust, collecting the extracted air, and feeding it into the RTO. We also changed ingredient transfer to closed pump suction instead of open pouring. The upgrade cost less than 200,000, significantly less than replacing the RTO with a larger unit, and it directly resolved the fence-line exceedance.

Second, breathing valves for tanks and containers offer the highest return on investment. If a 2-tonne solvent tank has no breathing valve or its valve has failed, one day of fugitive volatilization could account for a substantial portion of all stack emissions. Installing a breathing valve and nitrogen blanketing costs only several thousand per year.

Third, fix the locations of fence-line monitoring points and document them. This is not merely for inspections; it provides defensible evidence when disputes arise. Before and after the plant upgrade, we conducted 3 tests at the same point during the same period to create comparative data, which enabled us to substantiate our discussions with the authorities.

A Misconception That Must Be Clarified

Many printing plant owners believe that once treatment facilities at stack outlets are properly operated, the plant is compliant. This understanding is incomplete within the framework of pollutant discharge permitting.

The monitoring points specified in the pollutant discharge permit generally include both stack outlets and property-boundary points. These are fixed permit requirements rather than locations selected by the company. Without data from the property-boundary points, the plant has failed to fulfill its self-monitoring obligations.

Furthermore, the combined annual emission volume of organized and fugitive emissions must be reported. Some plants calculate only stack outlet emissions, resulting in an artificially low combined total and creating another compliance issue.

Further Reading

Air pollution is the most complex aspect of environmental compliance for printing plants and overlaps with several other environmental areas:

• Actual Disposal Cost Differences for 3 Types of Printing Waste Liquid—solid waste and hazardous waste operate under an entirely separate accounting framework from VOCs.
• Actual Costs of 3 Types of Printing Waste-Gas Treatment Processes: RTO/RCO/Activated Carbon—a horizontal comparison of treatment-process routes when selecting treatment facilities.
• The Revised Solid Waste Law Has Been in Effect for 5 Years, Yet Packaging and Printing Plants Remain Exposed—the penalty risks associated with solid waste reporting.
• 3 Hard Indicators for VOCs Treatment in Packaging Printing—another perspective focused on employee health that complements regulatory compliance.