4.4 Measuring and Removing Bioaerosols

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Del curso dictado por The Hong Kong University of Science and Technology

Introduction to Indoor Air Quality

35 calificaciones

The Hong Kong University of Science and Technology

Introduction to Indoor Air Quality

35 calificaciones

Course Overview: https://youtu.be/LLVb4FOn4uU This course provides a basic knowledge of an emerging area – Indoor Air Quality (IAQ) in buildings. Learners will realize the importance of maintaining proper IAQ. Characteristics associated with indoor air contaminants (IAC) are demonstrated, such as • Particulate matters (PM2.5, PM10) • Radon • Volatile organic compounds (VOCs) • Asbestos • Bio-aerosols, and more Safe exposure levels, resulting health effects, measurement techniques, mitigate and control measures of these IAC are discussed. Other important areas related to IAQ such as building ventilation systems, indoor flow characteristics, sick building syndrome, and thermal comfort are also covered in this course.

De la lección

Bioaerosols and Asbestos

In the last module of course, we look into the two other major indoor air contaminants - Bioaerosols and Asbestos. Staying in a clean environment does not mean the environment is comfortable. "Thermal Comfort" is also an issue that we need to consider. We also look into "Thermal Comfort" in this module.

4.1 Introduction to Bioaerosols5:42

4.2 Sources of Bioaerosols3:36

4.3 Health Effects of Bioaerosols7:46

4.4 Measuring and Removing Bioaerosols6:15

Conoce a los instructores

Christopher Chao
Chair Professor
Department of Mechanical and Aerospace Engineering
Edwin Tso
Research Assistant Professor
Department of Mechanical and Aerospace Engineering

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.

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