CDC recommends a minimum of an N95 filtering facepiece (FFP) respirator for SARS and AI.
N95 respirators are tested with NaCl particle 0.3 um. The efficiency of respirator media (filters) is generally greater when challenged with particles smaller than or larger than 0.3 um. This is due to basic particle physics. The next question is what is the size of SARS or AI particles? Would there be naked viral particles in the air or would they be much larger? I think the jury is out there . . . Perhaps a few naked particles and a bunch of larger particles!?
Now an additional question:: Is an N95 FFP respirator more protective than an N100 FFP respirator? Well, there is a difference in filtration efficiency (obvious . . . 95% vs 99.97%). The assigned protection factor (APF) for an N95 and an N100 filtering facepice (FFP) respirator is 10. What does APF mean? USA OSHA defines APF as: "The minimum expected workplace level of respiratory protection that would be provided by: a properly functioning respirator or a class of respirators; to properly fit-tested and trained users; when all elements of an effective respiratory protection program are established and ...
CDC recommends a minimum of an N95 filtering facepiece (FFP) respirator for SARS and AI.
N95 respirators are tested with NaCl particle 0.3 um. The efficiency of respirator media (filters) is generally greater when challenged with particles smaller than or larger than 0.3 um. This is due to basic particle physics. The next question is what is the size of SARS or AI particles? Would there be naked viral particles in the air or would they be much larger? I think the jury is out there . . . Perhaps a few naked particles and a bunch of larger particles!?
Now an additional question:: Is an N95 FFP respirator more protective than an N100 FFP respirator? Well, there is a difference in filtration efficiency (obvious . . . 95% vs 99.97%). The assigned protection factor (APF) for an N95 and an N100 filtering facepice (FFP) respirator is 10. What does APF mean? USA OSHA defines APF as: "The minimum expected workplace level of respiratory protection that would be provided by: a properly functioning respirator or a class of respirators; to properly fit-tested and trained users; when all elements of an effective respiratory protection program are established and are being enforced."
What does this mean in relation to an N95 or N100 FFP respirator? It means that irregardless of the filtration efficiency, you may expect a 1:10 reduction in particle concentration when properly wearing it and having passed a fit test. Why no difference? There are several reasons; however, I think the main reason the APF is the same is due to increased faceseal leakage as a result of increased resistance through an N100 filter.
So, is it safe to use an N95 FFP respirator? Yes. Is an N100 FFP respirator more protective? No. CDC recommends a minimum of an N95 FFP respirator for SARS and AI.
Regards,
Paul J
--------------------------
Sent from my BlackBerry . . . Please excuse my fumbling thumbs!
I am asking a more operational issue. Who should wear the N95 masks in resource limited settings where all staff cannot have access to them?. All staff working in TB clinics? Only where MDR TB is suspected? only for staff who are living with HIV? How are programs is resource limited settings going about this?
In resource limited settings, who should wear N95 masks?
*Definitely staff working in MDR units.*
*Staff working in TB clinics* because the MDR TB patients are diagnosed
by these TB clinics. They are their retreatment cases, treatment failures
and etc. New TB cases that may be infected for the first time with drug
resistant strains will be attending regular TB clinics before they are
diagnosed as MDR as Drug susceptibility taeting is not routinely done on new
cases. This means they will be diagnosed 6 months later or ven longer. In
addition where facility based DOTS is the norm, TB patients are coming daily
to the health facility hence inrecting with staff.
Health Facilities which were constructed years ago when the disease burden
was low and have not been expanded to cater for the increase patient
load (hence overcrowding) implies health acre workers are more at risk.
*Health care workers living with HIV:*
I wouldn't recommend that they work in an MDR unit, unless they are are not
in contact with patients at all. eg Administrative block, depending on how
its located relative to the TB wards, laboratory, admission room ...
In resource limited settings, who should wear N95 masks?
*Definitely staff working in MDR units.*
*Staff working in TB clinics* because the MDR TB patients are diagnosed
by these TB clinics. They are their retreatment cases, treatment failures
and etc. New TB cases that may be infected for the first time with drug
resistant strains will be attending regular TB clinics before they are
diagnosed as MDR as Drug susceptibility taeting is not routinely done on new
cases. This means they will be diagnosed 6 months later or ven longer. In
addition where facility based DOTS is the norm, TB patients are coming daily
to the health facility hence inrecting with staff.
Health Facilities which were constructed years ago when the disease burden
was low and have not been expanded to cater for the increase patient
load (hence overcrowding) implies health acre workers are more at risk.
*Health care workers living with HIV:*
I wouldn't recommend that they work in an MDR unit, unless they are are not
in contact with patients at all. eg Administrative block, depending on how
its located relative to the TB wards, laboratory, admission room, radiology
depart.
Ensure all health care workers wear the N965 masks when they interact with
patients (wards, or being in an enclosed room with the MDR TB patients).
Masks are availed to staff and are worn up to 3 months before disposal. (By
which time they are dirty, anyway).
I suppose the elastic loosen with time and may not be so effective in
sealing off the bacilli in the outside.......I stand to be corrected.
I would like to broaden this discussion to both N95 filtering facepiece respirators (certified by US CDC/NIOSH) and FFP2 filtering facepice respirators (certified by CEN, equivalent to N95s).
As Lorna has done, we must look at the hierarchy of controls. First administrative controls, then environmental controls, and finally, respiratory protection. The first part of administratrative controls is to understand risk of TB transmission in your facility. Next (though this is not an all inclusive list) would be identification and separation (in terms of time and/or space, where possible) of infectious or potentially infectious patients, education of patients, enforcement of proper cough etiquette/repiratory hygiene, education of staff (e.g., VCT, TB screening) and providing appropriate health care. Next, would be ensuring appropriate environmental controls (natural ventilation [more than just opening one window], mechanical ventilation, UVGI, etc.). Then, when the risk cannot be managed by administrative and environmental controls, you may develop a strategy such as that proposed by Lorna.
What are the two weakest "links" in any respiratory protection program? Training of staff and those cheap, thin rubber bands that limit the fit!!!
There is not a "one-size-fits-all" solution to this question.
I would like to broaden this discussion to both N95 filtering facepiece respirators (certified by US CDC/NIOSH) and FFP2 filtering facepice respirators (certified by CEN, equivalent to N95s).
As Lorna has done, we must look at the hierarchy of controls. First administrative controls, then environmental controls, and finally, respiratory protection. The first part of administratrative controls is to understand risk of TB transmission in your facility. Next (though this is not an all inclusive list) would be identification and separation (in terms of time and/or space, where possible) of infectious or potentially infectious patients, education of patients, enforcement of proper cough etiquette/repiratory hygiene, education of staff (e.g., VCT, TB screening) and providing appropriate health care. Next, would be ensuring appropriate environmental controls (natural ventilation [more than just opening one window], mechanical ventilation, UVGI, etc.). Then, when the risk cannot be managed by administrative and environmental controls, you may develop a strategy such as that proposed by Lorna.
What are the two weakest "links" in any respiratory protection program? Training of staff and those cheap, thin rubber bands that limit the fit!!!
There is not a "one-size-fits-all" solution to this question.
Regards,
Paul J
--------------------------
Sent from my BlackBerry . . . Please excuse my fumbling thumbs!
I would add some administrative suggestions to the discussion.
Based on our experience of respiratory protection program I would recommend to develop the prioritized lists of departments (rooms, floors), procedures and staff members based on risk level. According to this different level of priorities we quarterly distribute respirators for staff members, but amount of them per period of time is very different for everybody. Sure this assignment depends not only on risk level, but available resources as well. At least this prioritization helps to find way to provide better protection for HCW with funding available.
So not every staff member and not every time need to wear respirator. Actually every employee gets respirator, but administrator gets 1 for 3 months, nurse of smear positive ward - one for working shift and so on.
I absolutely agree with Paul Jensen: critical issue here is education and training of staff - where and when respirator should be used. Rearranging the TB facility according to IC principles should also help to limit the high risk areas and decrease the need for respirator use.
Dear All
At Tygerberg Hospital (Cape Town) the IPC recommendations are as follows
In admissions area (we see around 18 new cases a week on average) in the
hospital we recommend as part of the IPC protocol (negative ventilation
etc)- bearing in mind the cost of N95s
a) Triage as soon as possible for all those presenting with a cough
b) Staff wear an ordinary surgical mask when dealing with these
patients
On the wards risk prone procedures irrespective of patient status
(usually unknown) staff wear surgical masks
MDR-TB- cases are usually diagnosed and often known to N95 respirators
are recommended.
Now, our problem is the Fit Testing. It takes a long time, we need to
Fit Test everyone wearing an N95 and it just does not happen. Any ideas
about whether we can go ahead and use the N95s without fit testing? It
would make life easier.
One of the other big hospitals in Cape Town do not fit test and we are
trying to make a provincial policy.
Talk soon
Shaheen
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Lon)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box ...
Dear All
At Tygerberg Hospital (Cape Town) the IPC recommendations are as follows
In admissions area (we see around 18 new cases a week on average) in the
hospital we recommend as part of the IPC protocol (negative ventilation
etc)- bearing in mind the cost of N95s
a) Triage as soon as possible for all those presenting with a cough
b) Staff wear an ordinary surgical mask when dealing with these
patients
On the wards risk prone procedures irrespective of patient status
(usually unknown) staff wear surgical masks
MDR-TB- cases are usually diagnosed and often known to N95 respirators
are recommended.
Now, our problem is the Fit Testing. It takes a long time, we need to
Fit Test everyone wearing an N95 and it just does not happen. Any ideas
about whether we can go ahead and use the N95s without fit testing? It
would make life easier.
One of the other big hospitals in Cape Town do not fit test and we are
trying to make a provincial policy.
Talk soon
Shaheen
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Lon)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box 19063,
Tygerberg 7505, Cape Town
Thanks you for sharing but wonder if the surgical mask is not really a placebo? Or infact more harmful than useful. Given the cost of N95 masks I know many settings do not have them.
Moses Bateganya
Department of Global Health
University of Washington
Yes, possibly surgical masks are but then one has to decide whether any face cover or mask is better than NO mask. I think we have already had the debate on this one!
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Lon)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box 19063,
Tygerberg 7505, Cape Town
Thanks Dr. Paul J for a very extensive discussion.Very well explained. The
reason this thought came across was on the basis that viruses I thought are
very small and are even measured in nanometers. (Sorry for my ignorance,
and Im not too sure about the size of SARS). And if that is the case and
theoretically, a 0.3um filter will not be able to filter out a virus.
Thanks for everyone's helpful insight too.
Regards,
Grace
Paul A. Jensen, PhD, PE, CIH
Greetings! Thanks for the question, Grace.
expand commentCDC recommends a minimum of an N95 filtering facepiece (FFP) respirator for SARS and AI.
N95 respirators are tested with NaCl particle 0.3 um. The efficiency of respirator media (filters) is generally greater when challenged with particles smaller than or larger than 0.3 um. This is due to basic particle physics. The next question is what is the size of SARS or AI particles? Would there be naked viral particles in the air or would they be much larger? I think the jury is out there . . . Perhaps a few naked particles and a bunch of larger particles!?
Now an additional question:: Is an N95 FFP respirator more protective than an N100 FFP respirator? Well, there is a difference in filtration efficiency (obvious . . . 95% vs 99.97%). The assigned protection factor (APF) for an N95 and an N100 filtering facepice (FFP) respirator is 10. What does APF mean? USA OSHA defines APF as: "The minimum expected workplace level of respiratory protection that would be provided by: a properly functioning respirator or a class of respirators; to properly fit-tested and trained users; when all elements of an effective respiratory protection program are established and ...
4:39 PM, 8 Feb 2009 | Permalink
Moses Bateganya
I am asking a more operational issue. Who should wear the N95 masks in resource limited settings where all staff cannot have access to them?. All staff working in TB clinics? Only where MDR TB is suspected? only for staff who are living with HIV? How are programs is resource limited settings going about this?
Moses Bateganya
4:52 PM, 8 Feb 2009 | Permalink
Lorna Nshuti, MD
I'm no expert, but will give my experience:
expand commentIn resource limited settings, who should wear N95 masks?
*Definitely staff working in MDR units.*
*Staff working in TB clinics* because the MDR TB patients are diagnosed
by these TB clinics. They are their retreatment cases, treatment failures
and etc. New TB cases that may be infected for the first time with drug
resistant strains will be attending regular TB clinics before they are
diagnosed as MDR as Drug susceptibility taeting is not routinely done on new
cases. This means they will be diagnosed 6 months later or ven longer. In
addition where facility based DOTS is the norm, TB patients are coming daily
to the health facility hence inrecting with staff.
Health Facilities which were constructed years ago when the disease burden
was low and have not been expanded to cater for the increase patient
load (hence overcrowding) implies health acre workers are more at risk.
*Health care workers living with HIV:*
I wouldn't recommend that they work in an MDR unit, unless they are are not
in contact with patients at all. eg Administrative block, depending on how
its located relative to the TB wards, laboratory, admission room ...
12:31 AM, 9 Feb 2009 | Permalink
Paul A. Jensen, PhD, PE, CIH
Thanks for your insights, Lorna!
expand commentI would like to broaden this discussion to both N95 filtering facepiece respirators (certified by US CDC/NIOSH) and FFP2 filtering facepice respirators (certified by CEN, equivalent to N95s).
As Lorna has done, we must look at the hierarchy of controls. First administrative controls, then environmental controls, and finally, respiratory protection. The first part of administratrative controls is to understand risk of TB transmission in your facility. Next (though this is not an all inclusive list) would be identification and separation (in terms of time and/or space, where possible) of infectious or potentially infectious patients, education of patients, enforcement of proper cough etiquette/repiratory hygiene, education of staff (e.g., VCT, TB screening) and providing appropriate health care. Next, would be ensuring appropriate environmental controls (natural ventilation [more than just opening one window], mechanical ventilation, UVGI, etc.). Then, when the risk cannot be managed by administrative and environmental controls, you may develop a strategy such as that proposed by Lorna.
What are the two weakest "links" in any respiratory protection program? Training of staff and those cheap, thin rubber bands that limit the fit!!!
There is not a "one-size-fits-all" solution to this question.
Regards ...
1:11 AM, 9 Feb 2009 | Permalink
Grigory Volchenkov, MD
I would add some administrative suggestions to the discussion.
Based on our experience of respiratory protection program I would recommend to develop the prioritized lists of departments (rooms, floors), procedures and staff members based on risk level. According to this different level of priorities we quarterly distribute respirators for staff members, but amount of them per period of time is very different for everybody. Sure this assignment depends not only on risk level, but available resources as well. At least this prioritization helps to find way to provide better protection for HCW with funding available.
So not every staff member and not every time need to wear respirator. Actually every employee gets respirator, but administrator gets 1 for 3 months, nurse of smear positive ward - one for working shift and so on.
I absolutely agree with Paul Jensen: critical issue here is education and training of staff - where and when respirator should be used. Rearranging the TB facility according to IC principles should also help to limit the high risk areas and decrease the need for respirator use.
Hope it helps,
Dr. Grigory V. Volchenkov
Head Doctor
Vladimir Oblast TB Dispansery
Sudogodskoe shosse, 63
Vladimir 600023 RUSSIA
2:17 AM, 9 Feb 2009 | Permalink
S. Mehtar
Dear All
expand commentAt Tygerberg Hospital (Cape Town) the IPC recommendations are as follows
In admissions area (we see around 18 new cases a week on average) in the
hospital we recommend as part of the IPC protocol (negative ventilation
etc)- bearing in mind the cost of N95s
a) Triage as soon as possible for all those presenting with a cough
b) Staff wear an ordinary surgical mask when dealing with these
patients
On the wards risk prone procedures irrespective of patient status
(usually unknown) staff wear surgical masks
MDR-TB- cases are usually diagnosed and often known to N95 respirators
are recommended.
Now, our problem is the Fit Testing. It takes a long time, we need to
Fit Test everyone wearing an N95 and it just does not happen. Any ideas
about whether we can go ahead and use the N95s without fit testing? It
would make life easier.
One of the other big hospitals in Cape Town do not fit test and we are
trying to make a provincial policy.
Talk soon
Shaheen
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Lon)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box ...
3:15 AM, 9 Feb 2009 | Permalink
Moses Bateganya
Thanks you for sharing but wonder if the surgical mask is not really a placebo? Or infact more harmful than useful. Given the cost of N95 masks I know many settings do not have them.
Moses Bateganya
Department of Global Health
University of Washington
3:34 AM, 9 Feb 2009 | Permalink
S. Mehtar
Yes, possibly surgical masks are but then one has to decide whether any face cover or mask is better than NO mask. I think we have already had the debate on this one!
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Lon)
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box 19063,
Tygerberg 7505, Cape Town
3:58 AM, 9 Feb 2009 | Permalink
Grace Egos, MSPH
Thanks Dr. Paul J for a very extensive discussion.Very well explained. The
reason this thought came across was on the basis that viruses I thought are
very small and are even measured in nanometers. (Sorry for my ignorance,
and Im not too sure about the size of SARS). And if that is the case and
theoretically, a 0.3um filter will not be able to filter out a virus.
Thanks for everyone's helpful insight too.
Regards,
Grace
6:26 AM, 9 Feb 2009 | Permalink
Paul A. Jensen, PhD, PE, CIH
Dear Grace:
Once I get to Atlanta, I will ask the GHDOnline folks to post a filtration efficiency graphic.
Regards,
Paul J
--------------------------
Sent from my BlackBerry . . . Please excuse my fumbling thumbs!
4:53 AM, 11 Feb 2009 | Permalink