Standards & Testing

With increasing awareness of indoor air quality, air filtration and ventilation may be effective strategies in reducing exposure to air pollutants including bioaerosols. Exposure to bioaerosols is associated with a wide range of potential health effects including infectious diseases, allergies and others. The indoor concentration of bioaerosols can be reduced by properly designed and operated filtration system, such as residential HVAC and portable air cleaners, as well as natural and mechanical ventilation.

In this presentation, the results of an in-situ experimental evaluation of residential furnace filters and portable air cleaners are presented. Filters with filtration efficiency ranging from MERV8 to MERV 13 were selected for this experiment. Results are presented as a particle concentration decay for particle sizes representing typical indoor bioaerosols. The new ASHRAE 241 standard and its potential impact on residential filtration is discussed

The COVID-19 pandemic brought increased awareness to airborne infections and ways we can reduce transmission risk. We have also seen wildfire events cause air quality alerts across the US, drawing even more attention to the need for clean air. These are conversations that are being had more frequently and will not be going away soon. ASHRAE developed a new standard, 241, in record time to help guide building managers to best practices for controlling infectious aerosols. With this standard comes new guidelines for recommended filtration efficiencies and the use of mechanical vs. electret filter media. Changes in standards and development of new standards opens the industry to innovation for development of new materials that provide high performance. This talk will discuss the trends that are leading to the changes in air filtration standards, the changes to standards that are happening, and how the industry needs adapt to accommodate these changes.

Automated filter testers are designed for both the certification of respiratory protective devices (RPD) (respirators, masks, barrier face coverings, etc.) and quality control (QC) in the production of such devices. To certify respiratory protective devices, regional standards and regulations specify an aerosol particle size distribution (PSD) range and device classification based on the filtration performance tested in the mandated PSD range. For example, NIOSH 42 CFR Part 84 prescribes a polydisperse aerosol for testing with a count median diameter (CMD) of 185 � 20 nm and a geometric standard deviation of 1.60 or less, and define filter grades at 95%, 99% and 99.97% filtration efficiency. QC testing generally follows the practice. Using experimental test data using aerosols at three CMD’s (165 nm, 187 nm, and 197 nm) within the aerosol PSD range specified in NIOSH, this presentation demonstrates that efficiency results at one CMD differed significantly from those at another. We argue that rigorous QC testing of RPD and medias call for a more stringent requirement on the aerosol PSD range, and automated filter testers employed maintain consistent PSD throughout their service life. 

Changes in the efficiency or loading capacity of air filters may occur due to the influence of the carrier gas flow, especially rel. Humidity and Temperature. Taking this into account ISO Standards focus more on real conditions than in the past. As an example, the ISO 16890 contain a discharge cabinet for filters to simulate the possible degradation of filter efficiency due to ambient influences as e.g., moisture, Temperature or influences from separated particle. But still, most of the standards still require a 50% rel. Humidity and Temperatures between 20� C and 25� C regarding comparable results.

In reality, these filters are used in cars (Cabin air filters, Motor inlet filters), general ventilation systems of buildings or gas turbines or processes where the climatic conditions vary from 10% up to 100% Humidity and Temperatures between -20� C up to 50� C. Influences to the test result caused by different test conditions are thus not evaluated.

This is the reason why Palas® has developed the flat sheet media test bench MFP 3000 HF. With the new MFP 3000 HF, it is possible to set the relative humidity from 10 to 80 % and the temperature from -10 to 50� C. The inflow velocity has been extended as compared with standard models to a range of 4 cm/s – 2 m/s.

Test duct and sample taking:

Based on the internationally well-known MFP 3000, the HF Version is equipped with a new designed cooling and heating system which covers the whole test channel section including sample taking for particle detection to avoid condensation inside the test section and provide isothermal conditions. From the technical and operational point of view, the challenge was to get a wide range of air flow combined with a quick setting of rel. Humidity and Temperature at a high stability.

From the economical point of view, it is beneficial to operate such a test bench with a media test at low volume air flows to reduce energy cost for heating / cooling as well as humidification.

Aerosol measurement from 5 nm up to 40 �m:

A change in the climatic conditions during particle measurement of fractional efficiency may change the particle size distribution of the test Aerosol or cause condensation in the optics of the Aerosol Sensor. With the Promo® 3000 H Aerosol spectrometer it is possible to control Temperature even inside the Aerosol Sensors and thus ensure isothermal conditions for a reliable particle detection in the range of 200nm up to 40�m.

Additionally, the MPPS may be detected with the Palas® U-SMPS in a range of 5nm up to 1 �m.

Aerosol Generation:

The MFP 3000 HF is equipped with all necessary Aerosol generators to cover loading and fractional efficiency requirements as mentioned in e.g.

•     ISO 5011, dust loading ISO A2 Fine at 1000 mg/m� ,

•     ISO TS 11155-1, KCl low concentration for fractional efficiency and dust loading of ISO A2Fine at 75 m/m�

•     ISO 16890 KCl and DEHS in low concentrations for fractional efficiency and ISO A2 Fine at 140 mg/m� .

•     Other powders from practice at variable concentrations

This presentation outlines the technical set-up and climatization characteristics of the new test bench. We will show the possible changes of fractional efficiency and dust loading characteristics of the test sample due to the influence of rel. Humidity and Temperature.

Changes in the efficiency or loading capacity of air filters may occur due to the influence of the carrier gas flow, especially rel. Humidity and Temperature. Taking this into account ISO Standards focus more on real conditions than in the past. As an example, the ISO 16890 contain a discharge cabinet for filters to simulate the possible degradation of filter efficiency due to ambient influences as e.g., moisture, Temperature or influences from separated particle. But still, most of the standards still require a 50% rel. Humidity and Temperatures between 20�C and 25�C regarding comparable results.

In reality, these filters are used in cars (Cabin air filters, Motor inlet filters), general ventilation systems of buildings or gas turbines or processes where the climatic conditions vary from 10% up to 100% Humidity and Temperatures between -20�C up to 50�C. Influences to the test result caused by different test conditions are thus not evaluated.

This is the reason why Palas® has developed the flat sheet media test bench MFP 3000 HF. With the new MFP 3000 HF, it is possible to set the relative humidity from 10 to 80 % and the temperature from -10 to 50 �C. The inflow velocity has been extended as compared with standard models to a range of 4 cm/s – 2 m/s.

Test duct and sample taking:

Based on the internationally well-known MFP 3000, the HF Version is equipped with a new designed cooling and heating system which covers the whole test channel section including sample taking for particle detection to avoid condensation inside the test section and provide isothermal conditions. From the technical and operational point of view, the challenge was to get a wide range of air flow combined with a quick setting of rel. Humidity and Temperature at a high stability.

From the economical point of view, it is beneficial to operate such a test bench with a media test at low volume air flows to reduce energy cost for heating / cooling as well as humidification.

Aerosol measurement from 5 nm up to 40 �m:

A change in the climatic conditions during particle measurement of fractional efficiency may change the particle size distribution of the test Aerosol or cause condensation in the optics of the Aerosol Sensor. With the Promo® 3000 H Aerosol spectrometer it is possible to control Temperature even inside the Aerosol Sensors and thus ensure isothermal conditions for a reliable particle detection in the range of 200nm up to 40�m.

Additionally, the MPPS may be detected with the Palas® U-SMPS in a range of 5nm up to 1 �m.

Aerosol Generation:

The MFP 3000 HF is equipped with all necessary Aerosol generators to cover loading and fractional efficiency requirements as mentioned in e.g.

•     ISO 5011, dust loading ISO A2 Fine at 1000 mg/m�,

•     ISO TS 11155-1, KCl low concentration for fractional efficiency and dust loading of ISO A2Fine at 75 m/m�

•     ISO 16890 KCl and DEHS in low concentrations for fractional efficiency and ISO A2 Fine at 140 mg/m�.

•     Other powders from practice at variable concentrations

This presentation outlines the technical set-up and climatization characteristics of the new test bench. We will show the possible changes of fractional efficiency and dust loading characteristics of the test sample due to the influence of rel. Humidity and Temperature.