TB Infection Control

Dear Hugo,

We strongly discourage the use of portable HEPA filter air cleaning
machines based on those that we have seen around the world. Although
they sound good, and in theory they could work, there are all kinds of
pitfalls. Here are some of the major ones:

1) biggest problem is airflow limitation - the clean air delivery rate
(even if you believe what the manufacturer claims) is often so low
that if you calculate the number of room air changes (equivalent) per
hour, at most it is usually one or two, and at worst, a fraction of
one ACH.
2) short-circuiting of air from air cleaner exhaust back into intake -
because they are usually near each other - further reduces the amount
of air cleaning really going on.
3) Noise and drafts limit the flow rates that are acceptable in occupied rooms
4) Actual flow rates may be much lower than claimed by manufacturer.
5) Unless well-designed and well-built, room air may be sucked into
the box after the filter, another kind of short-circuiting, further
reducing the "effective" clean air delivery rate.
6) Air cleaners with UV in them are no better, often worse, suffering
from the same air flow limitations ...

Dear Hugo,

We strongly discourage the use of portable HEPA filter air cleaning
machines based on those that we have seen around the world. Although
they sound good, and in theory they could work, there are all kinds of
pitfalls. Here are some of the major ones:

1) biggest problem is airflow limitation - the clean air delivery rate
(even if you believe what the manufacturer claims) is often so low
that if you calculate the number of room air changes (equivalent) per
hour, at most it is usually one or two, and at worst, a fraction of
one ACH.
2) short-circuiting of air from air cleaner exhaust back into intake -
because they are usually near each other - further reduces the amount
of air cleaning really going on.
3) Noise and drafts limit the flow rates that are acceptable in occupied rooms
4) Actual flow rates may be much lower than claimed by manufacturer.
5) Unless well-designed and well-built, room air may be sucked into
the box after the filter, another kind of short-circuiting, further
reducing the "effective" clean air delivery rate.
6) Air cleaners with UV in them are no better, often worse, suffering
from the same air flow limitations

Bottom line - please do not waste money on portable room air cleaners
- unless you are sure that the machine is reliably delivering the
equivalent of at least 12 room air changes and has none of the major
pitfalls noted above. Most people do not have the resources to test
for all these pitfalls - best to avoid them altogether.

Upper room UV with a paddle fan is a more rationale and sustainable
solution, but only if there is expertise available to choose high
quality fixtures, install them properly, test them, and maintain them.
Of course, both mechanical and natural ventilation have similar needs
for expertise in planning and testing to be sure that they work, and
for maintenance to keep them working.

Ed

On Mon, Jul 9, 2012 at 12:53 PM, GHDonline (Hugo Siu) <> wrote:
> Hugo Siu added a new discussion to the TB Infection Control community.
>
> Title: HEPA Filters
>
> Discussion contents:
> "Dear Members,
> We need to know about portatil HEPA filter for use in a Private Clinic, Any company?
> Thanks
> Hugo
> Lima - Perú"
>
> --
> View this post online:
> <http://www.ghdonline.org/ic/discussion/hepa-filters/?id=10004&format=text&typ...>
>
> Unsubscribe or change your email notification settings:
> <http://www.ghdonline.org/users/edward-nardell-md/edit/>
>
> Contact the GHDonline team:
> <http://www.ghdonline.org/contact/>
>
> You can reply to this discussion by responding directly to this e-mail; it will be shared with all community members and posted as is. Files cannot be added via email attachment and must be uploaded directly to GHDonline.
>

Thanks

Hugo

Dr. Hugo Siu

Jefe del Area de Gestión de Calidad y Seguridad del Paciente

Dirección Médica

Clínica Anglo Americana

Anexo 1528

RPM: #994170973

________________________________________
De: GHDonline (Edward Nardell, MD)
Enviado el: lunes, 09 de julio de 2012 02:12 p.m.
Para: Hugo Siu
Asunto: Re: [TB Infection Control] HEPA Filters

Edward Nardell, MD replied to the discussion "HEPA Filters" in the TB Infection Control community.

Reply contents:
"Dear Hugo,

We strongly discourage the use of portable HEPA filter air cleaning
machines based on those that we have seen around the world. Although
they sound good, and in theory they could work, there are all kinds of
pitfalls. Here are some of the major ones:

1) biggest problem is airflow limitation - the clean air delivery rate
(even if you believe what the manufacturer claims) is often so low
that if you calculate the number of room air changes (equivalent) per
hour, at most it is usually one or two, and at worst, a fraction of
one ACH.
2) short-circuiting of air from air cleaner exhaust back into intake -
because they are usually near each other - further reduces the amount
of air cleaning really going on ...

Thanks

Hugo

Dr. Hugo Siu

Jefe del Area de Gestión de Calidad y Seguridad del Paciente

Dirección Médica

Clínica Anglo Americana

Anexo 1528

RPM: #994170973

________________________________________
De: GHDonline (Edward Nardell, MD)
Enviado el: lunes, 09 de julio de 2012 02:12 p.m.
Para: Hugo Siu
Asunto: Re: [TB Infection Control] HEPA Filters

Edward Nardell, MD replied to the discussion "HEPA Filters" in the TB Infection Control community.

Reply contents:
"Dear Hugo,

We strongly discourage the use of portable HEPA filter air cleaning
machines based on those that we have seen around the world. Although
they sound good, and in theory they could work, there are all kinds of
pitfalls. Here are some of the major ones:

1) biggest problem is airflow limitation - the clean air delivery rate
(even if you believe what the manufacturer claims) is often so low
that if you calculate the number of room air changes (equivalent) per
hour, at most it is usually one or two, and at worst, a fraction of
one ACH.
2) short-circuiting of air from air cleaner exhaust back into intake -
because they are usually near each other - further reduces the amount
of air cleaning really going on.
3) Noise and drafts limit the flow rates that are acceptable in occupied rooms
4) Actual flow rates may be much lower than claimed by manufacturer.
5) Unless well-designed and well-built, room air may be sucked into
the box after the filter, another kind of short-circuiting, further
reducing the "effective" clean air delivery rate.
6) Air cleaners with UV in them are no better, often worse, suffering
from the same air flow limitations

Bottom line - please do not waste money on portable room air cleaners
- unless you are sure that the machine is reliably delivering the
equivalent of at least 12 room air changes and has none of the major
pitfalls noted above. Most people do not have the resources to test
for all these pitfalls - best to avoid them altogether.

Upper room UV with a paddle fan is a more rationale and sustainable
solution, but only if there is expertise available to choose high
quality fixtures, install them properly, test them, and maintain them.
Of course, both mechanical and natural ventilation have similar needs
for expertise in planning and testing to be sure that they work, and
for maintenance to keep them working.

Ed

On Mon, Jul 9, 2012 at 12:53 PM, GHDonline (Hugo Siu) <> wrote:
> Hugo Siu added a new discussion to the TB Infection Control community.
>
> Title: HEPA Filters
>
> Discussion contents:
> "Dear Members,
> We need to know about portatil HEPA filter for use in a Private Clinic, Any company?
> Thanks
> Hugo
> Lima - Perú"
>
> --
> View this post online:
> <http://www.ghdonline.org/ic/discussion/hepa-filters/?id=10004&format=text&typ...>
>
> Unsubscribe or change your email notification settings:
> <http://www.ghdonline.org/users/edward-nardell-md/edit/>
>
> Contact the GHDonline team:
> <http://www.ghdonline.org/contact/>
>
> You can reply to this discussion by responding directly to this e-mail; it will be shared with all community members and posted as is. Files cannot be added via email attachment and must be uploaded directly to GHDonline.
>"

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