RE: Spore traps, d50 and particle technology

[Guest guest]

Wane,

Thanks for your feedback on the Air-O-Cells®.

Despite some possible inaccuracies in the descriptions given by others of the mechanisms at work, I take it that you do agree that a reduced velocity into the spore trap will result in a reduction of total number of spores captured (particularly those of lesser mass) when compared to a sample being drawn at the appropriate flow rate?

Best regards,

Phil S.

Spore traps, d50 and particle technology

Let's do what we can to get it right...... Please double-check your facts before posting to this group. Two serious mis-statements of late RE: AOCs (and other spore traps) reflect a lack of understanding of fundamental particle technology:1. "The Air-O-Cell cassette's jet-to-plate ratio will only capture spores and conidia larger than 2.5 microns. ...it does have the potential to give false negatives for several "Indicator Species" that have spores smaller than 2.5 microns." Nonsense! The d50 characteristic of any sampler is, in shorthand form, the mass mean aerodynamic diameter at which 50% of particles will be collected. The d50 curve is "S-shaped", with the middle of this flattened "S" crossing the 50% collection efficiency line. As a result, SOME particles of diameter <d50 WILL be collected and SOME of diameter >d50 will NOT be collected. How much is "some"? It depends on the slope of that "S-shaped" curve. 2. "The Air-O-Cell (AOC) works by impacting particles in a sticky medium. Airflow through the cassette affects particle velocity. If the particles are moving too quickly, some bounce off the surface and are carried away, and are not measured. If they are moving too slowly, the particles will hit but not stick to the medium, will roll off and be carried away, and again are not measured." Horsehockey! Lower velocities mean that more particles will follow the streamlines through the sampler and thus, never impact the target surface at all. They don't somehow strike it and then roll off. Please take the time to study the concepts of mass mean aerodynamic diameter, d50 collection efficiency, and streamlines before trying to contribute further to this line of discussion. Most of these same concepts are critical in understanding how air filters work. If you're going to make recommendations on sample collection for a specific situation, or make recommendations on filter selection, you'd better be fluent in "particle tech-speak". with my regards, Wane<><><><><><><><><><><><>Wane A. Baker, P.E., CIH, RPIHDirector, Air Quality Services"Bad air gets you down"MICHAELS ENGINEERING INC.811 Monitor Street, Suite 100PO Box 2377 La Crosse, Wisconsin 54602Phone , ext. 484Cell Fax mailto:wab@...On the web at: http://www.michaelsengineering.com "To love what you do and feel that it matters - how could anything be morefun?" - GrahamFAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.

[Guest guest]

See more detailed explanation and comments attached regarding cut point for Air-O-Cell.

As a side note, in field tests, the Air-O-Cell and Allergenco sampler performed the same in side by side field tests - not surprising as they have essentially the same shape and flow regimes [Havics, Tony: "A Field Comparison between the Allergenco7 Air Sampler and the Air-O-CellJ Cassettes in IAQ Studies", presented at Inter/Micro-2003, July 7, 2003, Chicago, IL.]

Tony

..................................................

"Tony" Havics, CHMM, CIH, PE

Executive Director of Technical Services

QEPI

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Indianapolis, IN 46239

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-----Original Message-----From: talk2ps@... Sent: Sunday, October 24, 2004 6:21 PMTo: iequality Subject: Re: Spore traps, d50 and particle technology

Wane,

Thanks for your feedback on the Air-O-Cells®.

Despite some possible inaccuracies in the descriptions given by others of the mechanisms at work, I take it that you do agree that a reduced velocity into the spore trap will result in a reduction of total number of spores captured (particularly those of lesser mass) when compared to a sample being drawn at the appropriate flow rate?

Best regards,

Phil S.

Spore traps, d50 and particle technology

Let's do what we can to get it right...... Please double-check your facts before posting to this group. Two serious mis-statements of late RE: AOCs (and other spore traps) reflect a lack of understanding of fundamental particle technology:1. "The Air-O-Cell cassette's jet-to-plate ratio will only capture spores and conidia larger than 2.5 microns. ...it does have the potential to give false negatives for several "Indicator Species" that have spores smaller than 2.5 microns." Nonsense! The d50 characteristic of any sampler is, in shorthand form, the mass mean aerodynamic diameter at which 50% of particles will be collected. The d50 curve is "S-shaped", with the middle of this flattened "S" crossing the 50% collection efficiency line. As a result, SOME particles of diameter <d50 WILL be collected and SOME of diameter >d50 will NOT be collected. How much is "some"? It depends on the slope of that "S-shaped" curve. 2. "The Air-O-Cell (AOC) works by impacting particles in a sticky medium. Airflow through the cassette affects particle velocity. If the particles are moving too quickly, some bounce off the surface and are carried away, and are not measured. If they are moving too slowly, the particles will hit but not stick to the medium, will roll off and be carried away, and again are not measured." Horsehockey! Lower velocities mean that more particles will follow the streamlines through the sampler and thus, never impact the target surface at all. They don't somehow strike it and then roll off. Please take the time to study the concepts of mass mean aerodynamic diameter, d50 collection efficiency, and streamlines before trying to contribute further to this line of discussion. Most of these same concepts are critical in understanding how air filters work. If you're going to make recommendations on sample collection for a specific situation, or make recommendations on filter selection, you'd better be fluent in "particle tech-speak". with my regards, Wane<><><><><><><><><><><><>Wane A. Baker, P.E., CIH, RPIHDirector, Air Quality Services"Bad air gets you down"MICHAELS ENGINEERING INC.811 Monitor Street, Suite 100PO Box 2377 La Crosse, Wisconsin 54602Phone , ext. 484Cell Fax mailto:wab@...On the web at: http://www.michaelsengineering.com "To love what you do and feel that it matters - how could anything be morefun?" - GrahamFAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.

[Guest guest]

Tony,

I appreciate your input. Is there a write-up available for the field comparison you mention between the AOC and the Allergenco7?

Best regards,

Phil S.

Spore traps, d50 and particle technology

Let's do what we can to get it right...... Please double-check your facts before posting to this group. Two serious mis-statements of late RE: AOCs (and other spore traps) reflect a lack of understanding of fundamental particle technology:1. "The Air-O-Cell cassette's jet-to-plate ratio will only capture spores and conidia larger than 2.5 microns. ...it does have the potential to give false negatives for several "Indicator Species" that have spores smaller than 2.5 microns." Nonsense! The d50 characteristic of any sampler is, in shorthand form, the mass mean aerodynamic diameter at which 50% of particles will be collected. The d50 curve is "S-shaped", with the middle of this flattened "S" crossing the 50% collection efficiency line. As a result, SOME particles of diameter <d50 WILL be collected and SOME of diameter >d50 will NOT be collected. How much is "some"? It depends on the slope of that "S-shaped" curve. 2. "The Air-O-Cell (AOC) works by impacting particles in a sticky medium. Airflow through the cassette affects particle velocity. If the particles are moving too quickly, some bounce off the surface and are carried away, and are not measured. If they are moving too slowly, the particles will hit but not stick to the medium, will roll off and be carried away, and again are not measured." Horsehockey! Lower velocities mean that more particles will follow the streamlines through the sampler and thus, never impact the target surface at all. They don't somehow strike it and then roll off. Please take the time to study the concepts of mass mean aerodynamic diameter, d50 collection efficiency, and streamlines before trying to contribute further to this line of discussion. Most of these same concepts are critical in understanding how air filters work. If you're going to make recommendations on sample collection for a specific situation, or make recommendations on filter selection, you'd better be fluent in "particle tech-speak". with my regards, Wane<><><><><><><><><><><><>Wane A. Baker, P.E., CIH, RPIHDirector, Air Quality Services"Bad air gets you down"MICHAELS ENGINEERING INC.811 Monitor Street, Suite 100PO Box 2377 La Crosse, Wisconsin 54602Phone , ext. 484Cell Fax mailto:wab@...On the web at: http://www.michaelsengineering.com "To love what you do and feel that it matters - how could anything be morefun?" - GrahamFAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.

[Guest guest]

Other than the abstract which didn't say alot no. I'm looking to do an article in the future.

-----Original Message-----From: talk2ps@... Sent: Monday, October 25, 2004 8:26 PMTo: iequality Subject: Re: Spore traps, d50 and particle technology

Tony,

I appreciate your input. Is there a write-up available for the field comparison you mention between the AOC and the Allergenco7?

Best regards,

Phil S.

Spore traps, d50 and particle technology

Let's do what we can to get it right...... Please double-check your facts before posting to this group. Two serious mis-statements of late RE: AOCs (and other spore traps) reflect a lack of understanding of fundamental particle technology:1. "The Air-O-Cell cassette's jet-to-plate ratio will only capture spores and conidia larger than 2.5 microns. ...it does have the potential to give false negatives for several "Indicator Species" that have spores smaller than 2.5 microns." Nonsense! The d50 characteristic of any sampler is, in shorthand form, the mass mean aerodynamic diameter at which 50% of particles will be collected. The d50 curve is "S-shaped", with the middle of this flattened "S" crossing the 50% collection efficiency line. As a result, SOME particles of diameter <d50 WILL be collected and SOME of diameter >d50 will NOT be collected. How much is "some"? It depends on the slope of that "S-shaped" curve. 2. "The Air-O-Cell (AOC) works by impacting particles in a sticky medium. Airflow through the cassette affects particle velocity. If the particles are moving too quickly, some bounce off the surface and are carried away, and are not measured. If they are moving too slowly, the particles will hit but not stick to the medium, will roll off and be carried away, and again are not measured." Horsehockey! Lower velocities mean that more particles will follow the streamlines through the sampler and thus, never impact the target surface at all. They don't somehow strike it and then roll off. Please take the time to study the concepts of mass mean aerodynamic diameter, d50 collection efficiency, and streamlines before trying to contribute further to this line of discussion. Most of these same concepts are critical in understanding how air filters work. If you're going to make recommendations on sample collection for a specific situation, or make recommendations on filter selection, you'd better be fluent in "particle tech-speak". with my regards, Wane<><><><><><><><><><><><>Wane A. Baker, P.E., CIH, RPIHDirector, Air Quality Services"Bad air gets you down"MICHAELS ENGINEERING INC.811 Monitor Street, Suite 100PO Box 2377 La Crosse, Wisconsin 54602Phone , ext. 484Cell Fax mailto:wab@...On the web at: http://www.michaelsengineering.com "To love what you do and feel that it matters - how could anything be morefun?" - GrahamFAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.