Can the fresh air system use chemical filters to filter outdoor odors?

Yes, but it depends on where the odor comes from and what its main ingredients are.

When the fresh air system introduces outdoor air, if there are odor sources nearby, these odors may enter the room with the fresh air. Chemical filters can target some gaseous components, but they are not a panacea. Different odor sources correspond to different chemicals and require different treatment options. If you don't first understand the main ingredients and directly choose a 'deodorizing filter', the effect may not be ideal. For specific selection logic, please refer to Discussion on why chemical filters should be selected according to the target gas .

Identify gases by source

Outdoor odor is not a single thing, it comes from different sources and its ingredients vary greatly.

Traffic emissions. Car exhaust contains carbon monoxide, nitrogen oxides, hydrocarbons, etc. This type of contamination usually does not have an obvious 'odor' but may be perceptible under certain conditions.

Industrial emissions. Chemical plants, printing and dyeing plants, pharmaceutical plants, etc. may emit acidic gases, organic solvents, sulfides, etc. This type of pollution often has a distinct odor.

Wastewater treatment facilities. Hydrogen sulfide, ammonia, mercaptans, etc. may be released near sewage stations and pumping stations. The odor threshold of these gases is very low, and trace amounts can be detected.

Catering fumes. Catering areas may emit oil fumes and volatile organic compounds with obvious odors.

Waste disposal facilities. Garbage stations and landfills may release mixed odors such as sulfide, ammonia, and organic acids.

Gases from different sources have different combinations and need to be identified separately. One type of deodorizing medium cannot be used to cover all outdoor pollution sources. For specific sampling methods, please refer to whether to do air sampling before choosing a chemical filter . Discuss

Evaluate the location of new air outlets

The location of the new air outlet directly affects the introduced pollution load.

Whether the new air outlet is close to the pollution source. If the fresh air outlet is close to the road, drainage outlet, sewage station or other source of odor, the concentration of introduced pollution may be higher. Adjusting the position of the new air outlet is sometimes more economical than adding a filter section. For specific evaluation methods, please refer to The factory is close to the source of pollution, and the discussion on how to match the relocation of the air inlet with chemical filtration is discussed.

The influence of wind direction and time of day. The pollution load may be different in different wind directions and at different times. When designing, the most unfavorable conditions should be considered, or room for adjustment should be reserved.

Filters cannot compensate for all unreasonable inlet conditions. If the fresh air outlet faces the pollution source, or is too close to it, the filter material may be consumed quickly even if a chemical filter section is added. In this case, priority should be given to adjusting the inlet position or adding preprocessing.

Separate sensory and concentration goals

Odor control and concentration control are two different goals.

Odor reduction does not mean that all specified gases meet the requirements. The human sense of smell is very sensitive to some gases but not to others. Hydrogen sulfide can be smelled at very low concentrations, but carbon monoxide is almost odorless but poses a health risk.

If the project has specific gas concentration requirements, individual testing and verification are required. The treatment effect cannot be judged simply by 'not smelling the odor'. Outlet detection should use a method suitable for the target gas and check the detection limit.

Arrange entrance and exit inspections according to project objectives. The fresh air inlet and supply air outlet are sampled separately to determine the effect of the filter section. At the same time, the wind direction, time period and emission conditions are recorded to facilitate subsequent analysis. For specific detection methods, please refer to Discussion of sampling points for chemical filter performance verification .

Configuration of chemical filtration section

After confirming the target gas and fresh air outlet conditions, the configuration of the chemical filtration section can be evaluated.

Choose a medium that targets the main ingredient. If the main component is sulfide, you need to select the corresponding medium; if it is ammonia or amines, you need a medium suitable for alkaline gas; if it is mixed pollution, you may need a layered configuration or composite filter material. involving MAU box-type chemical filters , the location of the filter section is usually determined during the unit design stage. For fresh air projects with

Consider particle prefiltration. The dust in the fresh air will cover the chemical medium and shorten the service life. Setting up appropriate particle prefiltration before the chemical filtration section can reduce the media burden. Please refer to the specific division of labor Discussion on the division of labor between chemical filters and primary filters .

Check system resistance. Adding a chemical filtration section will increase the total system resistance. When selecting a fan, it is necessary to add up the initial resistance and final resistance of filters at all levels to check whether the working point is acceptable. For specific accounting methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

Reserve sampling and maintenance channels. Sampling ports are provided before and after the filtration section to facilitate subsequent tracking of outlet concentration changes. The channel for replacing filter media should also be confirmed during the design stage. Supporting The local circulation system, interfaces and maintenance methods of the FFU supporting chemical filter also need to be checked.

Project judgment example

An office building is adjacent to a sewage treatment facility. After fresh air is introduced, odor often appears in the room.

The preliminary plan is to add a conventional activated carbon filter section to the fresh air unit. After running, it was found that the odor was reduced, but it was still noticeable in certain wind directions.

Investigation process: Take samples at the fresh air inlet and air supply outlet respectively, covering different wind directions and time periods. Test results show that the main odor-causing components are hydrogen sulfide and a small amount of mercaptans, and conventional activated carbon has limited adsorption capacity for such gases.

Adjustment plan: Replace with chemical filter media targeting sulfides, and evaluate the location of new air outlets to avoid the main pollution wind direction. After adjustment, the outlet concentration and sensory properties were significantly improved, and the problem of fresh air odor was under control.

This case illustrates: Fresh air deodorization requires first identifying the main components and then selecting the corresponding medium. You cannot choose based on the words 'deodorizing' alone. involving For the configuration of the chemical filter product series , it is recommended to provide the source information and test results to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s fresh air deodorization package

The core of fresh air deodorization is to match the source of outdoor odor, fresh air outlet conditions and filter section configuration.

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 need to deal with outdoor odors, the source information, fresh air outlet location, target gas and system conditions can be combined to help check the location of the filter section and the media type. 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 outdoor source, target gas, 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.