Is there an exact way to prove ventilation will help clean the air and protect us from contamination from germs?
An
article in the ECRI Health Product Evaluation Book that concerns a
very interesting and scientific way of estimating this question:
To
estimate the number of people who will become infected ( C ) by any
airborne disease when they are in a room and then exposed to one or
a number ( L ), of infected people we must use this equation.
The correlation of this equation with different infection control
techniques was studied:
A closed room contains an infectious patient producing 1.25 to 250 viable droplet nuclei per hour ( q ).
The
room has one source of clean air, a high efficiency-filter air cleaner
( such as an NQ Clarifier ) operating
at a certain airflow ( Q ) or room air changes.
A healthcare worker or any person ( S = susceptible person ) breathing
0.5 L per breath at 12 breaths per minute ( p ) who enters the room
to care for the patient for 15 minutes ( t ).
The risk for the standard HVAC system with 10 cfm of clean air is
between - 1 : 150 to 1 : 1.4
The risk with an added air purifier with 300 cfm of clean air is between
- 1 : 4,600 to 1 : 25
The risk for an added air purifier with 1200 cfm of clean air is between
- 1 : 18,000 to 1 : 92
Formula is: C = S x ( 1 - e ( -Lqpt/Q ) ) The risk in the equation
is directly related to the actual airflow volume as it relates to
the 300 cfm base air flow used in the above test and equation results
shown.
It is quite obvious that a unit should be used in any of these rooms,
at any air flow rate over the CDC recommended 12 air changes ( more
is indeed proved to be better ).
There also has been numerous articles, news or media programs and
research done, which shows the above risk numbers to be conservative
and the documented infections are actually greater.
