TB Infection Control
Cross-post: length of usage of N95 mask indoor?
Rajbir Singh, a member of the DR TB community asked for guidance on N95 masks: how many days one N 95 mask can be used in indoor settings? Is there any study?
My reply is copied below, and the original discussion can be viewed at this link: http://www.ghdonline.org/drtb/discussion/n-95-respiratorsmasks/
Dear Dr Singh!
Your question deals with a complex issue and the answer is "it depends" on many factors. The official answer is "follow manufacturer's instructions." The following comments relate solely to TB and not to influenza or other microorganisms spread by large droplets or contact. There is a manuscript in preparation showing that the filters maintain their certified filtration efficiencies after extended (weeks) of usage. The qualitative part of the study identifies the straps (rubber bands --> underwear elastic) as the weakest part of the respirator.
Personally, I generally use two N95 or FFP2 respirators (with exhaust valves) per week. I use one in the morning and another one in the afternoon. I wrap each one in a paper towel and allow them to dry over night. Occasionally, the cheap, blue rubber bands will break in less than one week.
How do you know how well a model fits? Well, if it is loose on your face (straps are stretched), you probably do not have a good fit. Fit testing is good to tell you if a particular model fits you when it's new out-of-the-box! Why don't we fit test folks AFTER they wear a respirator for a while? I don't know; however, I think it would be great if folks would start collecting such data!!!
I am currently on travel with limited Internet access.
Regards,
Paul J
Attached resource:
Grigory Volchenkov, MD
Dear Dr. Singh,
This is a very important question in TB Infection Control community.
According to NIOSH (The National Institute for Occupational Safety and Health), the reuse of N95 (or FFP2) respirators is permitted for occupational TB prevention provided the respirators have not been damaged, soiled, or breathing resistance becomes great enough to cause discomfort to the wearer or integrity of the respirator has not been compromised.
Apparently some suppliers of the new disposal respirators are informing clients that respirators can only be used one time and then must be replaced. According to expert opinion it is based mostly on commercial reasons.
The weak part of N95s is usually strips, not filter.
In my TB hospital in Vladimir, Russia, nurse of SS+ ward needs 1 respirator for 1 - 2 shifts, doctors - 4 - 6 for month. It depends on workload and actual time being spent in high risk zones.
I recommend you this CDC GLs on respiratory protection:
http://www.cdc.gov/niosh/docs/99-143/#step3
Hope it helps,
Dr. Grigory Volchenkov, Vladimir, Russia
12:49 PM, 6 Jun 2009 | Permalink
Rajbir Singh
Dear Dr. Paul,
Many thanks for sharing your experience.
In my view manufacturer's opinion may be influenced by commercial interests
or to keep themself safe. It is useful to correlate with practical
experiences.
Your experience is useful to plan our MDR TB project.
I take up weak strap issue with manufacturer.
Thanks for addressing my query inspite of your busy schedule.
Best wishes and kind regards,
Rajbir Singh
India
6:02 AM, 8 Jun 2009 | Permalink
Rajbir Singh
Dear Dr. Gregory,
Many thanks for the help.
We also plan to use N95 mask for counselors based in hospital and in field.
Later has to counsel patients and families in their homes located in crowded
slum dwellings. In both settings contact period with TB patients may be
significant.
The practice followed in your hospital is quite feasible in our settings
(which combines hospital with community based approach).
Thanks for informing me the problem of weak strip and I address the same
with manufacturer here. One N95 mask costs less than half a euro or 27=00
Indian rupee here.
Best wishes and kind regards,
Dr. Singh
6:34 AM, 8 Jun 2009 | Permalink