Atmospheric monitoring

Question 1

What is a personal sampler

Answer 1

Attached to the person

Question 2

What is a static sampler

Answer 2

positioned in work area
continuous sampling
mains or battery powered pumps

Question 3

What document details standard methods of sampling

Answer 3

MDHS series - methods for determination of hazardous substances

Question 4

Short term sampling

Answer 4

spot, snap or gran sampling
take immediate sample of air, pass through a chemical agent that responds to chemical being monitored
or direct reading instrument

Question 5

Long term sampling

Answer 5

personal or static samplers

Question 6

Considerations for sampling strategy / method

Answer 6

type of air contamination from initial appraisal
people affected - representative group or random sampling
frequency of measuring - depends on hazard, acute / chronic effects, exposure limits, previous results
technique - depends on hazard, purpose of sample

Question 7

measurement for chronic hazard

Answer 7

continuous personal dose measurement

spot readings at selected locations / times

Question 8

measurement for acute hazard

Answer 8

continuous rapid response personal monitoring

spot readings at selected locations / times

Question 9

measurement for safe entry

Answer 9

direct reading instrument

Question 10

direct reading instrument examples

Answer 10

combustible gas detector
oxygen meter
ultraviolet photo ionisation detector (PID)

Question 11

advantages of direct reading instrument

Answer 11

info at time of sampling

quick detection

Question 12

disadvantages of direct reading instrument

Answer 12

only measure specific chemical classes
not designed for less than 1 ppm
can be affected by other substances - false readings
need to be operated by qualified person

Question 13

reasons for atmosphere monitoring

Answer 13

health risk assessment
compliance with WELs
help design controls
check effectiveness of controls
info for employees
indicate need for health surveillance
establish in house standards

Question 14

Info sources

Answer 14

labels on containers
safety data sheets
HSE publications
technical info from trade assocs
accident records
health surveillance records
absence rates
staff complaints

Question 15

stain tubes

Answer 15

contain inert material with reagent for substance being tested for
glass tubes
passive or via pump (manual or powered)

Question 16

advantages of stain tubes

Answer 16

easy to use
easy to read
wide range of tubes available
low cost

Question 17

disadvantages of stain tubes

Answer 17

limited shelf life
false reading from other chemicals
safe disposal issues
limited accuracy
depends on skill of operator

Question 18

bags & canisters

Answer 18

evacuate air before use
use where constant concentration
bag is chemically inert
sent to lab for analysis

Question 19

Tyndall lamp

Answer 19

light that shows dust floating in the air

Question 20

factors influencing health effects of dust

Answer 20

nature of the dust
particle size
exposure time
airborne concentration

Question 21

where is the breathing zone

Answer 21

300 mm in front of and around face

Question 22

dust filtration sampling system

Answer 22

filter suitable for dust being sampled
sampling head - holds the filter, prevents problems ref wind
tubing
pump - to maintain smooth flow at required rate, light for personal sampling system

Question 23

types of sampling head

Answer 23

protected
cyclone
cowl head

Question 24

protected head sampler

Answer 24

no problems ref orientation or wind speed

best in workplace conditions

Question 25

cyclone head sampler

Answer 25

cyclones simulate nose / mouth

used for respirable dust sampling

Question 26

cowl head sampler

Answer 26

for fibre sampling
open faced filter
cowl faces downwards

Question 27

types of sampling pump

Answer 27

piston / compressed chamber
rotary vane
diaphragm

Question 28

piston / compressed chamber pump

Answer 28

volume depends on number of pump strokes
relies on manual operation
cannot be used for dust sampling

Question 29

rotary vane pump

Answer 29

flow rate measured with integral flow meter

sample volume = flow rate x time

Question 30

diaphragm pump

Answer 30

sample volume = number of diaphragm moves

Question 31

other pump considerations

Answer 31

dust explosion risk, therefore must not be source of electrical ignition
battery capacity
serviced regularly
pump cleaning

Question 32

filter types

Answer 32

paper - cheap but absorb water
glass fibre - cheap, high particle retention but shed fibres
silver - low chemical interference but expensive
plastic membrane - good for use with microscope but high static, poor dust adhesion
PVC - low chemical interference but high static, poor dust adhesion

Question 33

filter weighing

Answer 33

pre-weighed and weighed again after sampling

matched weight - contains 2 filters but only one collects dust. Both weighed at lab

Question 34

MDHS dust sampling method

Answer 34

decide on sample head
select clean dry head
fit with required filter
attach to pump
have blank samplers available
use blanks as control
attach to worker with head in breathing zone
check often for correct operation
at end, record flow rate and duration
fit protective cover over head and remove from worker
remove filter and send for analysis

Question 35

dust measuring analysis

Answer 35

gravimetric
physical
chemical

Question 36

gravimetric analysis

Answer 36

measure weight of dust collected
weigh filter before and after
calibrated weighing device
calculate dust concentration

Question 37

physical analysis

Answer 37

techniques inc
xray fluorescence spectroscopy
xray diffraction
infra red
atomic absorption

Question 38

chemical analysis

Answer 38

analysis of metal dusts

Question 39

fibre analysis

Answer 39

use microscope
difficult to accurately count fibres
use phase contrast microscope to help see fibres - enhances contrast of fibres on filter
use polarising filters also

Question 40

passive personal samplers

Answer 40

no pump
some change colour to indicate contamination
light
easy to use
activated charcoal to collect solvents

Question 41

active personal samplers

Answer 41

worn by worker
pump fitted to belt
tube attached near to collar

Question 42

activated charcoal tubes

Answer 42

absorbs vapours
tube sealed with plastic caps
sent off for analysis

Question 43

sampling technique requirements

Answer 43

minimum 75% collection efficiency for contaminant being tested for
collect enough to analyse
collection means compatible with analysis technique
minimum on-site preparation
equipment / technique does not create a hazard to worker

Question 44

vapour analysis techniques

Answer 44

remove contaminant from material that absorbed it
use solvent (carbon disulphide) or heat to desorbe into gas
analyse vapour

Question 45

types of vapour analysis

Answer 45

infrared spectrometry - used for organic chemicals
ultraviolet spectrometry - metals
atomic absorption spectrometry - determines actual concentration levels
chromatography - colour separation of substances in mixtures
gas liquid chromatography - solid / liquid vapourised and separated in an inert gas stream
xray diffraction - xrays diffracted when pass through substance, diffraction pattern analysed

Question 46

formula for dust concentration

Answer 46

weight gain in filter divided by total volume of air sampled

mg / m3

Question 47

advantages of Tyndall lamp

Answer 47

very fine dust not visible to naked eye, lamp shows this up
can see source of dust
use as first stage analysis
qualitative technique
easy to use
minimal training needed

Question 48

disadvantages of Tyndall lamp

Answer 48

provides immediate info only

does not measure particle size