Hello everyone. In this video,
we will talk about how to measure and remove bioaerosols.
There are 4 methods to measure the concentration and composition of bioaerosols.
Filtration and microscopy, cascade impactors,
biosensors, and real-time analyzers with UV fluorescence.
Filtration and microscopy is the simplest method for sampling.
Bioaerosol particles are captured by a filter when air passes through.
It requires microscopic inspection for analysis after collecting a sample,
so the process can be tedious.
There are different filters porosities to
select in order to collect different sizes of particles.
Cascade impactors are the most common samplers.
This method collects bioaerosol particles onto
a solid or a semi-solid collection surface.
Air is pumped into an impactor containing a series of impact plates at a low speed.
The air speed increases at every stage so
that large particles are deposited in the first stage,
and smaller particles are collected through the remaining plates.
When measuring bioaerosols using cascade impactor,
appropriate agar medium is placed on
these impact plates to collect bioaerosols particle samples for analysis.
For example, TSA is an agar to collect bacteria.
MEA is used to collect fungi.
A biosensor is an analytical device containing an immobilized biological material,
such as enzyme and an antibody which can specifically interact with
a target bioaerosol and produce
electrical signals to be measured by an electronic transducer.
It can identify many viruses and bacteria,
and the measurement time is short.
The result is directly recorded in controllers or our computers.
Biosensors are treated as an essential sensor for future bioaerosol detection.
Real-time analyzers with UV fluorescence are real-time measuring instruments
applied to detect bioaerosol particles from 0.5 microns to 20 microns.
Normally, a pair of laser beams is
utilized to measure the scattered light intensity of a particle,
and the aerodynamic diameter of the particle.
Since components of bioaerosol particle fluorescence when excited with a UV light source,
the analyzers can distinguish bioaerosol particles easily.
After introducing the bioaerosols measurement methods,
now we will talk about bioaerosols removal equipment.
These include filtration, electrostatic precipitation,
and ozone disinfection of ventilation.
The first method to remove bioaerosols is by filtration.
The filtration mechanism of filtering
bioaerosols is the same as filtering particulate matters.
Diffusion, interception, and impaction are applied depending on the particle size.
Bioaerosols are different form of particle matters in several ways such as shape,
size distribution, surface characteristics, and motility.
Some bioaerosols grow in the presence of moisture.
So, they may grow on the filter surface.
As a result, the removal efficiency of a filter may be affected.
Electrostatic precipitation is commonly used to remove particles from air streams.
The device consists of 2 stages.
One we have corona wires and one with collection plates.
When air flows into the device,
bioaerosol particles in the air are charged by the corona wires.
Then, the bioaerosol particles are collected onto the collection plate filled with agar.
Research shows that ozone is
an antimicrobial agent that is active against bacteria, fungi, viruses.
The antimicrobial activity of ozone is based on a strong oxidizing ability.
Ozone is generated by high voltage current like corona discharge,
or a UV light at 185 nanometer.
However, while ozone reacts with other air contaminants,
harmful byproducts may be produced.
As a result, in order to use ozone to remove bioaerosol particles,
an ozone decomposition unit,
or a sufficient unit is needed to protect people from direct exposure to ozone.
To conclude, in this video we introduced several bioaerosols measurement methods,
and the removal equipment.
Christopher ChaoAdjunct Professor
