Should I do an air sampling before choosing a chemical filter?

There is no unified answer to this question, but there is a judgment principle: if the pollution components are unclear, or the project has strict control requirements, sampling is usually a worthwhile step.

Some projects already know what the target gas is, such as specific solvents in the process exhaust and acidic gases brought by external inputs, so they can be selected directly based on the known components. But if you only smell an odor and know that 'there is pollution', but you can't tell what gas it is and what its concentration is, then choosing a filter element directly will be risky. After the installation, the effect is not satisfactory, and if we go back to investigate, the time and cost will increase.

Sampling is not to follow the process, but to answer several specific questions: what gas is to be processed, what is the approximate concentration at the inlet, where is the main source, and how to set the outlet target. Only when these questions are clear can the selection be based on. For specific selection logic, please refer to Discussion on why chemical filters should be selected according to target gases .

Make it clear what the sample will answer

Before taking a sample, think clearly about what problem this test will solve.

Identify gas components. If you don't know what the gas is, sampling can help determine the main components. For example, if there is an odor at the site, common odor-causing substances such as TVOC, sulfides, ammonia, and organic acids can be detected to gradually narrow the scope.

Determine the source. By taking samples at the fresh air inlet, return air outlet, and key workstations, we can determine whether the pollution comes from external input or internal release, as well as the transmission path. For specific investigation methods, please refer to Discussion on how to choose a chemical filter when the components and sources of odor are unclear .

Establish an acceptance baseline. For projects with clear export requirements, sampling can record the background concentration before treatment as a benchmark for subsequent comparisons.

Evaluate filter media suitability. After obtaining the inlet concentration and composition, the suitability of the candidate filter material can be checked to determine whether it can meet the export target.

Sampling without a target may result in a bunch of data that cannot be used for selection. First determine the questions you want to answer, and then design a sampling plan.

Choose a representative location

Different sampling locations reflect different pollution conditions.

Fresh air entrance. Reflects external input gas load. Sampling at this location is important if the project needs to address external contamination.

Return air outlet. Reflects the overall condition of indoor air, including a mixture of internal releases and external inputs. Suitable for evaluating loop filtration needs.

Near key workstations or equipment. Reflect local pollution conditions. If a location is particularly sensitive to a gas, or if pollution sources are concentrated nearby, sampling data here is more direct.

Inlet and outlet paired sampling. If a filtration section has been installed, inlet-outlet paired sampling can evaluate filtration effectiveness. However, attention should be paid to the sampling time to match, otherwise the efficiency calculation may be distorted when the inlet concentration fluctuates. For specific methods, please refer to Discussion of sampling points for chemical filter performance verification .

Sampling should cover representative time periods. If contamination is intermittent, sampling times should include the period during which contamination occurs. The data measured during the pollution-free period cannot represent the actual load.

Keep comparable records

The data obtained through sampling must be used for model selection and subsequent comparison, and the records must be complete.

Sampling time, place and method. This basic information must be recorded clearly. Sampling results at different times and locations are interpreted in different ways.

Production status and ventilation conditions. The operating status of the equipment, ventilation volume, and door zone status during sampling will all affect the results. This information can help determine the representativeness of the data.

Detection methods and detection limits. Different detection methods have different detection limits. If the result is lower than the detection limit, it should be stated whether it is 'not detected' or 'lower than the method detection limit' and cannot be directly regarded as zero concentration.

Changes in working conditions. If working conditions change during the sampling period, such as equipment starting and stopping, ventilation adjustments, this should be noted in the record to facilitate subsequent analysis.

involving For the MAU box-type chemical filter fresh air project, it is recommended to reserve a sampling port in the fresh air section to facilitate follow-up tracking.

Sampling is not required but can reduce risk

Some project conditions are clear, the target gas is clear, and the type can be selected directly.

The target gas and concentration range are already known. For example, regarding specific solvents in process exhaust, bill of materials and safety data sheets can provide information, as can air testing data. In this case, you can directly select based on known ingredients.

The source of pollution is single and the ingredients are stable. If there is only one clear source of pollution on site, the composition is not complex, and there is already operational experience, the sampling process can also be reduced.

However, it is recommended to arrange sampling in the following situations:

• Key workstations or equipment are sensitive to gases and have strict export requirements.

• There are many unknown gases, or the composition may change with the process

• It is necessary to evaluate the filtering effect and establish an acceptance baseline

• The filter section has been installed but the effect is not satisfactory. The reason needs to be investigated.

In these cases, sampling can reduce the risk of selecting the wrong filter material and provide a basis for subsequent acceptance.

Project judgment example

A certain workshop reported a peculiar smell, but the source and ingredients could not be explained.

Preliminary investigation found that the odor appeared after specific processes and was more obvious near the equipment operating area. However, there is no clear target gas and the concentration range cannot be determined.

Treatment method: Arrange sampling first. Take samples near the equipment, at the return air outlet, and at the fresh air inlet to cover the period when the odor occurs. The test results show that the main component is certain types of organic solvent volatiles, and the concentration range is above the detectable level.

Based on this result, chemical filter media for this type of organic gas was selected, and the air volume and installation space were checked. After the trial, the outlet concentration and odor will be confirmed to be improved before finalizing the formal plan.

This case illustrates: When the ingredients are unknown, sampling can help narrow the scope and avoid blind selection. For specific trial methods, please refer to Discussion of how to set clear success conditions for chemical filter trials .

Key points for selection and acceptance inspection

About Aili Industrial’s sampling and selection support

Sampling is a preliminary step in model selection, but how to map the sampling results to the product plan requires checking the target gas, concentration, air volume, and installation conditions.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For projects that require sampling first, the sampling results, system conditions and installation space can be combined to assist in checking the filter material type and structural configuration. When the filter is matched with MAU, FFU, EFU and other equipment, the resistance, interface and maintenance methods can be confirmed uniformly.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . Providing sampling results, target gases and system conditions with your inquiry will help confirm the appropriate filtration solution. The specific selection is subject to the technical documents and test results confirmed by the project.