Indoor odors are different from fresh air inlets and may come from internal materials, workstation releases, return air accumulation, or gas mixing. Locations and time periods along the air path should be compared, and media should not be judged based on just two odor descriptions. Smell is a clue, not a conclusion.

Don’t rush to attribute it to the new trend.

In many cases, when there is a peculiar smell in the room, the first reaction is to check the fresh air. But if the fresh air entrance smells different from the indoor smell, it means that the problem is most likely not at the entrance itself, or not just at the entrance. The composition of the gas brought in by fresh air may have changed after passing through the air supply duct, room circulation and internal release. What needs to be answered at this time is: What is added to the indoor air and at what stage is it added? It is impossible to tell whether it is a change in concentration or a change in ingredients based on the difference you smell with your nose.

Split the air path into several comparable points

To investigate odor differences, a more effective approach is to set up points along the air path: fresh air inlet, supply air outlet, return air outlet, near the work station, and exhaust outlet. Each point records the odor characteristics, occurrence period and corresponding operation. If there is no obvious smell at the fresh air inlet but a strong smell at the return air outlet, it means there is an internal release source; if there is an odor at the air supply outlet but it is heavier at the return air outlet, it means there is both external input and internal superposition; if the smell only appears at a specific work station, focus on checking the materials and operations of that work station. Regarding the method of distinguishing outdoor and internal pollution, please refer toHow to distinguish whether workshop pollution comes from outside or inside?。

Pay attention to the time difference and working conditions when sampling

One thing that is easily overlooked in odor surveys is that the data at different points may not correspond to the same mass of air. From the fresh air inlet to the indoor work station, the air flow needs to pass through a path and time. If the sampling is not synchronized, the comparison may be the status of different periods. In addition, the odor performance may be completely different under different working conditions such as production, cleaning, shutdown, and door opening. Try to compare various points under the same working conditions and record operating events. Only test when the smell is obvious and not after the smell disappears. It is easy to miss short-term loads. For ideas on sampling during the boot period, please refer toThere is a peculiar smell only when the machine is turned on. At what time should the gas be measured?。

Different smells may also mean different ingredients

The two odor descriptions are different, sometimes reflecting changes in the composition of the gas, not just the concentration. Fresh air may be dominated by acidic gases emitted from outdoor traffic or industry, and indoors may be superimposed with organic components released by cleaning agents, adhesives, or equipment. If you only measure the total amount of TVOC, you may not be able to see the difference in ingredients. In this case, it is necessary to determine the possible range of components based on the bill of materials, and then select the corresponding detection method. For the selection dilemma when there is only total data, please refer toOnly the total amount of TVOC has no gas components. Can I directly choose a chemical filter?。

Aili industrial supporting equipment

For issues such as odor differences, when matching, we usually recommend that customers first test several points on the air path, and then decide where to place the filter section and what ingredients to configure. If internal release is the main cause, local filtration may be required at the workstation or equipment end; if the return air accumulation is obvious, chemical filtration in the circulation section is more appropriate; if fresh air input is dominant, the gas phase section of the fresh air outlet needs to be checked. Aili Industry can provide selection packages for box-type, flat-plate and V-type chemical filtration products. For box-type MAU packages, please refer toMAU box type chemical filter , product series can be viewedChemical filter product range . Equipment-side applications can adopt the form of chemical filtration FFU, integrating chemical adsorption layer and HEPA/ULPA particle filtration. The structure of chemical first and then particles is suitable for areas with AMC control requirements. The V-shaped structure provides a larger filtration area in the same box space, helping to control surface speed and resistance under circulating air volume. The manufacturing end covers motors, fans, control systems, sheet metal and complete machine assembly. The location of the filter section and the air supply conditions can be checked together during the matching stage. The specific gas effect and replacement cycle still need to be verified based on the corresponding configuration data and on-site working conditions. The actual results are subject to on-site leak detection and gas detection results.

Related questions and answers

There is no smell at the fresh air inlet, but there is smell inside the room. Is there no need to check the fresh air?
It cannot be completely ruled out. The fresh air gas may have a low concentration but different composition, or may react with indoor substances to produce odor. It is recommended to sample fresh air and indoors at the same time to compare the components rather than just the intensity of the odor.

Are different smells and different concentrations the same thing?
no. Differences in odor may come from changes in composition or from differences in concentration. Judgment requires ingredient data and cannot rely solely on sensory description.

Can Aili Industrial help determine the location of the filter section?
The air path sampling results and internal release source judgment can be combined to check the configuration of the new air outlet, circulation section or local filtration at the equipment end. The specific plan needs to be confirmed based on on-site working conditions and product data.

Related articles

• Multiple workstations use different solvents, how to divide chemical filtration?

• Will more people coming in and out affect gaseous pollution control?

• How long does it take to reassess gas contamination in a renovated clean room?

• If the clean room pressure difference is qualified, why can external gas still enter?

Key points for selection and acceptance inspection