Particle Filters

Question 1

What are the five mechanisms of fiber filter?

Answer 1

gravitational settling, impaction, diffusion, interception, electrical forces

Question 2

what is the typical fiber filter thickness?

Answer 2

150 to 500 microns

Question 3

which mechanism is for coarse particles?

Answer 3

settling, impaction, electrical forces

Question 4

which mechanism is for ultrafine particles?

Answer 4

diffusion and interception

Question 5

which filter has higher pressure drop?

Answer 5

membrane filters

Question 6

how do you decrease the cut diameter for membrane filters?

Answer 6

we increase the face velocity

Question 7

what are the sizes that can enter our respiratory tract?

Answer 7

for inhalable, less than 100 microns
for thoracic, less than 30 microns
for respirable, less than 10 micrond

Question 8

what are pre-separators?

Answer 8

equipment that filters out particles via inertial impaction

Question 9

what kind of conditions are special sampling requirements applied?

Answer 9

tropical - high DBT, cold - freezing inlet, mountains

Question 10

what is a whole air inlet?

Answer 10

all cloud droplets are drawn into the inlet and evaporated hence slightly heated

Question 11

what kind of equipment should we use for sampling coarse particles?

Answer 11

isokinetic aerosol splitter

Question 12

when can we neglect the particle over-and under sampling?

Answer 12

if Stk < 0.01 and the ratio of nozzle velocity and flow velocity is within .2 and 5

Question 13

what should be the maximum RH operating condition for field sampling?

Answer 13

40%

Question 14

what are different aerosol drying methods?

Answer 14

diffusion dryer, membrane dryer, dilution dryer

Question 15

which dryer uses a dry air supply?

Answer 15

membrane dryer

Question 16

which aerosol drying method is recommended for tropical observatories?

Answer 16

dilution

Question 17

why is heating not used?

Answer 17

it can cause evaporation of semi-volatile particles

Question 18

how to decrease the ultrafine particle loss due to diffusion?

Answer 18

pipes should be as short as possible, should use stainless steel and maintain laminar conditions

Question 19

what operating conditions should be done for coarse particles?

Answer 19

vertical pipes, if not possible use high air flow

Question 20

how should sample air be brought into the lab?

Answer 20

through a vertical stack

Question 21

how high should the aerosol inlet above ground level?

Answer 21

5 to 10 m

Question 22

what kind of inlets should be used?

Answer 22

PM10 inlet