Unit 4 Lecture 22 Topic 1

Question 1

How did people stay safe from coronavirus?

Answer 1

They practiced good hygiene by washing hands with soap and water for at least 20 seconds, stayed home and away from others when ill, practiced physical distancing (e.g., avoiding crowds, minimizing non-essential trips from home, keeping 2- metres distance from others), and cleaned and disinfected frequently touched surfaces.

Question 2

What are the two categories of masks?

Answer 2

Medical and non-medical (cloth face coverings).

Question 3

When should you wear a medical mask?

Answer 3

If you’re experiencing covid-19 symptoms and will be in close contact with others or going out to access medical care.

Question 4

When should you wear a non-medical mask or cloth face covering?

Answer 4

To help stop the spread of COVID-19, or when it is not possible to maintain a 2-metre physical distance from others.

Question 5

Respirators (Filtering face-piece respirator [FFR]) come in what forms?

Answer 5

Surgical, commercial, and industrial.

Question 6

Surgical respirators:

Answer 6

Must meet the minimum requirements of filtration performance (ie, >95% efficient at filtering 0.3-μm particles). They require fit-testing so they do not leak around the mask and are tested against fluid resistance and flame resistance. They are used for medical, surgical and other high-risk procedures in health care. N95 respirators can be an example of a surgical mask (unless it is a commercial N95).

Question 7

Commercial respirators:

Answer 7

Used in businesses to reduce risks to the user and to others primarily from COVID-19. They have a >94% submicron particle filtration.

Question 8

Industrial respirators:

Answer 8

Used in construction, welding and renovations to protect the wearer from inhaling dust, welding fumes, fiberglass, etc.

Question 9

Surgical masks:

Answer 9

Loose-fitting, disposable devices that create a physical barrier between the mouth and nose of the wearer and potential contaminants in the immediate environment. They may be referred to as surgical, isolation, dental, or medical procedure masks. Not all face masks are regulated to be surgical masks.

Question 10

What are the two main properties required for face masks?

Answer 10

High particle filtration and sufficient air permeability.

Question 11

Why must face masks have high particle filtration capabilities?

Answer 11

To prevent transmission of respiratory droplets and bio-aerosols.

Question 12

Why must face masks have sufficient air permeability?

Answer 12

To allow breathing.

Question 13

Can surgical respirators or masks be reused?

Answer 13

They are not intended to be reused, however, due to shortages during Covid-19, they often are.

Question 14

What are the five main mechanisms in the filtration of respiratory droplets and aerosols?

Answer 14

Gravity sedimentation, inertial impact, interception, diffusion, and electrostatic attraction.

Question 15

Large respiratory droplets:

Answer 15

About 5 μm to 10 μm in size. Due to being larger and heavier they fall onto the surface of the mask below (gravity sedimentation) or hit a solid surface and are stopped rather than continue in the air stream (inertial impact).

Question 16

Smaller respiratory droplets:

Answer 16

0.1 μm to 1 μm in diameter. Diffusion and mechanical interception are the major mechanisms of filtration by the fibres of the mask.

Question 17

Tiny bio-aerosols:

Answer 17

In the nanometer range (<100 nm). Electrostatic attraction is the major method for capture. Particles are negatively charged and fibres are positively charged.

Question 18

Outermost layer of surgical face masks:

Answer 18

Waterproof, helps to repel fluids such as saliva and mucus.

Question 19

Middle layer of surgical face masks:

Answer 19

Filters and prevents particles or pathogens (eg, viruses) over
a certain size penetrating the mask from the outside.

Question 20

Innermost layer of surgical face masks:

Answer 20

Absorbent layer to absorb respiratory droplets from the wearer.

Question 21

What are surgical masks and respirators made from?

Answer 21

Polypropylene fibres that are positively charged are melt-blown or spun-bonded into a non woven fabric. The microfibres with diameters ranging from 2−10 μm form a porous structure.

Question 22

What are health Canada’s guidelines for non-medical face masks?

Answer 22

A homemade or purchased face mask or covering should be made of at least 3 layers. 2 of these layers should be tightly woven material fabric, such as cotton or linen. The third (middle) layer should be a filter-type fabric, such as non-woven polypropylene fabric. As well, the mask must be large enough to completely and comfortably cover the nose, mouth and chin without gaping while still allow for easy breathing. It must fit securely to the head with ties or ear loops and be comfortable and not require frequent adjustments. It must also be changed as soon as possible if damp or dirty and maintain its shape after washing and drying.

Question 23

What types of filters can be found in non-medical face masks?

Answer 23

Non-woven polypropylene fabric, which can be found as a craft fabric, or the non-woven fabric that’s used to make some reusable shopping bags can be used, or a disposable filter can be inserted into a pocket on the mask.

Question 24

Why is dimensional stability important in choosing fabrics for making multi-layer cloth masks?

Answer 24

If fabrics have different dimensional stabilities they may become distorted during washing and lead to poor fit and function.

Question 25

Why is fabric density and fabric weight important in choosing fabrics for making multi-layer cloth masks?

Answer 25

Denser and heavier fabrics have better particle filtration due to the smaller spaces between the yarns or fibres but they also have higher breathing resistance (lower air permeability). A balance of particle filtration and breathing resistance is
necessary to be functional.

Question 26

Why is fabric elasticity important in choosing fabrics for making multi-layer cloth masks?

Answer 26

As they stretch, spaces open up between the yarns reducing filtration efficacy. If used, a stretchy fabric should be combined with a more stable layer.

Question 27

What are the pro’s and con’s of brushed or napped surfaces on face cloths?

Answer 27

Although this may trap droplets well, it could cause irritation against the wearer’s nose or mouth so it is best used as an outer or middle layer. When used, the raised surface should be positioned towards the face and include at least one additional layer between the raised surface and the wearer’s face.

Question 28

Why is yarn selection important in choosing fabrics for making multi-layer cloth masks?

Answer 28

Yarns made from staple fibres (spun/staple yarns) may have better filtration properties as they decrease the open spaces between and within the yarns. Texturized multi-filament yarns may also achieve this.

Question 29

Why is fabric softness important in choosing fabrics for making multi-layer cloth masks?

Answer 29

Comfortability.

Question 30

Why is moisture retention important in choosing fabrics for making multi-layer cloth masks?

Answer 30

Fabrics that move or hold moisture away from the face may be more comfortable.

Question 31

Why are fabric finishings important in choosing fabrics for making multi-layer cloth masks?

Answer 31

Coated or laminated fabrics may be undesirable due to their high breathing resistance and the chance that chemicals used may be unsuitable for direct contact with the mouth and nose.