Clarifying 18 Issues Regarding VOCs Management

Since the release of the "Standards for Unorganized Emission Control of Volatile Organic Compounds" (GB 37822-2019) and two industry standards - the VOCs emission standards for the coating and pharmaceutical industries, as well as the "Key Industry Volatile Organic Compound Comprehensive Control Plan" issued by the National Environmental Protection Department, the concepts, standards, and governance ideas of VOCs have been unified. They should be relatively clear and operational. However, in daily work, many people still have confusion about the concepts and even apply the wrong standards.

The following are 18 common questions collected and discussed in the form of questions and answers.

1. Question: Has the concept of VOCs been unified?

Answer: Correct. The national standard has defined volatile organic compounds (VOCs) as organic compounds that participate in atmospheric photochemical reactions, or organic compounds determined according to relevant regulations. This concept is simple and concise. The previous definitions with temperature conditions are outdated and only applicable to the circumstances specified by the standards.

Moreover, volatile organic compounds (VOCs) is a general concept, and specific pollutants have separate control items.

2. Question: Has the concept of TVOC been updated?

Answer: Correct. The early concept of TVOC originated from the "Indoor Air Quality Standard" (GB/T18883-2002), referring to volatile organic compounds that are analyzed using Tenax GC or Tenax TA sampling, non-polar chromatographic columns (with a polarity index less than 10), and have retention times between n-hexane and n-hexadecane, C6-C16. Now it refers to measuring individual VOCs substances in the air using the prescribed monitoring methods, adding them up to obtain the total amount of VOCs substances. The requirements are to add up 90% or more of the individual substances. The monitoring methods are hj 644 and hj 734.

3. Question: Is VOCs the same as TVOC?

Answer: Incorrect. VOCs is the general term for volatile organic compounds, and the "S" is not always. TVOC is the total volatile organic compounds and is a specific pollutant item. In several standards in Guangdong, there is a total VOCs, which is actually synonymous with TVOC.

4. Question: Does the "Standards for Unorganized Emission Control of Volatile Organic Compounds" only cover unorganized emissions and does not apply to organized emissions?

Answer: Incorrect. If the operation is not carried out in a sealed container, all initial emissions of VOCs are in the form of unorganized emissions. This standard is about how to manage unorganized emissions of VOCs, trying to convert unorganized emissions into organized emissions and providing process control and final emission standards.

5. Question: Is non-methane total hydrocarbons not VOCs?

Answer: Incorrect. When characterizing the overall emission of VOCs, according to industry characteristics and environmental management requirements, total volatile organic compounds (TVOC) and non-methane total hydrocarbons (NMHC) can be used as pollutant control items. Thus, here, VOCs, TVOC, and NMHC have been unified. The former is a general concept, while the latter two are specific pollutant control items. It is incorrect to artificially separate them.

6. Question: In environmental impact assessment, the characteristic pollutant is non-methane total hydrocarbons, and the current monitoring TVOC is incorrect?

Answer: This statement is incorrect. According to the 2018 new air quality guidelines, there are no conventional environmental air quality factors. According to the values in the table, TVOC refers to the indoor air quality standard. Non-methane total hydrocarbons refer to the detailed explanations or other standards, and none of them are the requirements of the guidelines.

7. Question: Why are the evaluation values of total volatile organic compounds (TVOC) and non-methane total hydrocarbons (NMHC) different?

Answer: That's because the monitoring methods are different. Non-methane total hydrocarbons (NMHC) uses the reduction method, measuring total hydrocarbons and methane separately, and then subtracting.

Note: The above translation is based on the provided text and may not capture all nuances of the original Chinese.

Total Volatile Organic Compounds (TVOC) is measured using the addition method, where each component needs to be measured separately and then added together to obtain the total value

8. Question: Under normal circumstances, which of the two, total volatile organic compounds (TVOC) or non-methane total hydrocarbons (NMHC), has a higher measurement value?

Answer: Generally, it is non-methane total hydrocarbons. The addition method for measuring TVOC requires conducting component analysis first, adding up the components that account for at least 90% of the total. However, in reality, 24 or 35 components are measured, and even the adsorbent 1 detects C6-C16.

Non-methane total hydrocarbons use the subtraction method, which has lower accuracy than TVOC, but the overall level is well controlled.

This is similar to a pollution source census. Only when each individual project investigation is accurate can the total be accurate; otherwise, the calculation of the pollution discharge coefficient is more appropriate for the overall situation.

From the differences in the current evaluation of environmental air quality, the eight-hour average of total volatile organic compounds is 0.6 milligrams per cubic meter, which is converted to a daily average of 0.6 x 2 = 1.2 milligrams per cubic meter. Non-methane total hydrocarbons use detailed explanations or the local standards of Hebei Province as the daily average value of 2.0 milligrams per cubic meter.

This also indirectly indicates one issue: under normal circumstances, the measured value of non-methane total hydrocarbons is approximately twice that of TVOC.

9. Question: Are plastic polymers considered low VOCs materials?

Answer: Incorrect. VOCs materials refer to materials with a VOCs mass fraction of 10% or more, as well as organic polymer materials.

10. Question: Can the production process of low VOCs materials not collect exhaust gas?

Answer: Yes. The "Key Industry Volatile Organic Compound Comprehensive Treatment Plan" has a requirement that for processes where the VOCs content (mass ratio) of the raw materials and auxiliary materials is less than 10%, there is no requirement to take measures for unorganized emissions collection. Here, it is "can", and of course, the management department may consider it necessary and say "cannot".

11. Question: Can VOCs exhaust gas be collected randomly?

Answer: Incorrect. For those using external exhaust hoods, the wind speed at the measurement point must not be less than 0.3 m/s.

Moreover, factory areas and surrounding areas should be set up with unorganized monitoring points, and the control should be carried out according to the standards.

12. Question: Can low-concentration and low-rate organic exhaust gas emission treatment facilities be exempted?

Answer: Yes. If enterprises use products that comply with the national regulations on low-VOCs content coatings, inks, adhesives, etc., and the emission concentration is stable and meets the regulations, the corresponding production processes can be exempted from requiring the construction of end-of-pipe treatment facilities.

It is also "can", but when management requires it, it can also be "cannot". However, one thing to note is that if the initial emission rate of VOCs is greater than or equal to 3 kilograms per hour, and in key areas, it is greater than or equal to 2 kilograms per hour, the exhaust gas must be collected and treated to ensure stable emission concentration and also implement removal efficiency control, with a removal efficiency of no less than 80%.

13. Question: Is the height of the exhaust stack necessarily 15 meters?

Answer: Not necessarily. For safety considerations and special process requirements, exceptions can be made.

14. Question: Is UV photolysis completely rejected?

The country has classified UV photolysis as a low-efficiency treatment device, but it has not rejected its effectiveness in odor removal and odor elimination. If combined with other measures, it can also be an effective treatment method.

UV photolysis + activated carbon adsorption, combined with an activated carbon combustion device, is also a good choice. Not all enterprises can install RTO, and not all enterprises can afford RTO.

15. Question: Are there any specific standards for organized VOCs emissions with exhaust pipes?

Answer: Yes. According to the "Volatile Organic Compound Unorganized Emission Control Standard", for collected and treated organized emissions, those with industry standards should follow the industry standards, and those without industry standards should follow the comprehensive standards.

16. Question: In current environmental impact assessment and management, is the strictest "Volatile Organic Compounds (VOCs) Emission Standard for the Furniture Manufacturing Industry" (DB 44/814-2010) used to judge the VOCs emission standards of other industries correct?

Answer: Incorrect.

Firstly, the concept of VOCs in the furniture industry is already inconsistent with the current national standards; it is not the current concept. Secondly, the past management was stricter in the absence of regulations, and now there are clear national standards that can be implemented. Before clear local standards are established, one cannot refer to different categories; thirdly, many industries have no similarity to the furniture industry in terms of VOCs generation principles; fourthly, the monitoring method for total VOCs in the furniture industry is based on the determination method of total volatile organic compounds (TVOC) in indoor air, and the accuracy is not high.

Strangely enough, we knew early on that we should not refer to that, and it was originally an expedient measure. However, due to inertia or something, now that there are clear standards, many people still forcibly implement this reference standard. In fact, since there are clear standards (whether strict or not), they should be implemented.

17. Question: Is there an exemption range for the total VOCs substitution?

Answer: Yes. Taking Guangdong Province as an example, the "Notice of the Guangdong Provincial Department of Ecology and Environment on Doing a Good Job in the Management of Volatile Organic Compounds Total Indicator for Key Industry Construction Projects" requires that for production and service activities that generate VOCs emissions, they should be carried out in enclosed spaces or equipment, and a clear total substitution source should be specified. That is to say, those below 300 kilograms per year are exempted. Other provinces follow the local policies.

18. Question: Is the "Pollution Prevention and Control Law" Article 45, "Production and service activities that generate volatile organic compounds waste gas should be carried out in enclosed spaces or equipment and facilities should be installed and used in accordance with regulations"， the污染防治 facilities just the end-of-pipe treatment facilities?

Answer： Not necessarily. Waste gas collection and high-level emission are also污染防治 facilities. In addition， "installing and using in accordance with regulations" cannot be detailedly specified by the law； it can only be stipulated by standards and departmental normative documents.

Views on VOCs evaluation and rectification：

1. Through a cycle of exploration， VOCs management has returned.

VOCs went through the flourishing period of the Spring and Autumn Warring States with various schools of thought competing and arguing about their own concepts， then the Five Dynasties and Ten Kingdoms period， when everything was chaotic due to the invasion of the Five Huns， and then entered the tripartite confrontation of VOCs， NMHC， and TVOC. Now it has basically unified.

In the early environmental impact assessment reports， non-methane total hydrocarbons (NMHC) was used as the emission factor， while TVOC was used as the quality evaluation factor. At that time， there were no documents confirming that they could both represent VOCs， but now it seems to be scientific.

After segmentation understanding and management without a clear reason， recent several national standards and policy documents have conceptualized the concept of VOCs that many people previously considered as specific pollutants， and have designated specific items as non-methane total hydrocarbons (NMHC) and total volatile organic compounds (TVOC) and characterized them by industry.

As long as the industry characteristics are confirmed， in the environmental impact assessment reports， we can boldly characterize the VOCs emissions as non-methane total hydrocarbons or TVOC， including the subsequent total requirements. Then， will you still say that a certain project only mentioned non-methane total hydrocarbons (NMHC) and no VOCs evaluation and emission standards？ 

2. Why has it been going on for so long， and still feel that the VOCs management using non-methane total hydrocarbons indicators is more accurate and direct?

Gong Gong said： Huang Shiren fought in and out， it's just the measuring instrument is different. What we are talking about is VOCs， it's just characterized by non-methane total hydrocarbons or TVOC.

This means that if you want a broader scope, use non-methane total hydrocarbons (NMHC). If you want a narrower scope, use TVOC.

Take a look at these several monitoring methods and you will understand:

1. Non-methane total hydrocarbons (NMHC): For fixed pollution sources, use HJ 38; for environmental air, use HJ 604.

2. Total volatile organic compounds (TVOC): For fixed pollution sources, use HJ 734; for environmental air, use HJ 644.

3. TVOC in indoor air: Appendix C of GB/T 18883-2002.

4. Guangdong local standard total VOCs: Use the monitoring method for TVOC in indoor air.

As mentioned above, the monitoring of non-methane total hydrocarbons (NMHC) is a subtractive method, relatively coarse, with simple and mature methods, and has high accuracy over a wide range.

Total volatile organic compounds (TVOC) is an additive method, more detailed and accurate. Theoretically, it should be more accurate, but in actual monitoring, it is less accurate over a wide range.

This is determined by the monitoring conditions. The main measurement range of indoor air monitoring methods lies in the C6-C20 range, while the definition of TVOC in the "Volatile Organic Compounds Unorganized Emission Control Standard" is more strict. More than 90% of the components must enter. Under the current technical conditions and monitoring conditions, how easy is it to do this?

When the technical conditions have not yet reached a high level, using non-methane total hydrocarbons (NMHC) for simple and direct management is a relatively scientific approach.

III. Correctly understand several exemption conditions.

The production process of low-VOCs materials can be exempted from collecting exhaust gas, which means that the process using raw materials with VOCs content (mass ratio) lower than 10% does not require the adoption of unorganized emission collection measures.

If enterprises use coatings, inks, adhesives, etc. that comply with the national regulations on low-VOCs content products, and the emission concentration is stable and meets the regulations, the corresponding production processes do not need to build end-of-pipe treatment facilities. However, there is one issue to note: if the initial emission rate of VOCs is greater than or equal to 3 kilograms per hour, and in key areas greater than or equal to 2 kilograms per hour, it must be collected and treated to ensure stable emission concentration and also implement removal efficiency control, with a removal efficiency of no less than 80%.

For the total VOCs total amount management of key industries' construction projects, those with a total amount of less than 300 kilograms per year can be exempted. Currently, this only applies to Guangdong Province.

IV. Environmental Impact Assessment should completely solve several unreasonable problems.

Environmental Impact Assessment writes unreasonable things in, and one refection clears up the problem, but it should be cleaned up. For example, "double 90", for example, furniture still needs double 90. A factory gives a quantity of one kilogram. These historical products should not reappear in the national standards after their emergence.

Because impossible things are written in, only forcing people to fake them is possible.

This article is excerpted from the First Environmental Protection Network

The pictures are from the Internet

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