Atmospheric monitoring Flashcards

1
Q

What is a personal sampler

A

Attached to the person

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2
Q

What is a static sampler

A

positioned in work area
continuous sampling
mains or battery powered pumps

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3
Q

What document details standard methods of sampling

A

MDHS series - methods for determination of hazardous substances

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4
Q

Short term sampling

A

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

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5
Q

Long term sampling

A

personal or static samplers

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6
Q

Considerations for sampling strategy / method

A

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

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7
Q

measurement for chronic hazard

A

continuous personal dose measurement

spot readings at selected locations / times

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8
Q

measurement for acute hazard

A

continuous rapid response personal monitoring

spot readings at selected locations / times

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9
Q

measurement for safe entry

A

direct reading instrument

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10
Q

direct reading instrument examples

A

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

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11
Q

advantages of direct reading instrument

A

info at time of sampling

quick detection

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12
Q

disadvantages of direct reading instrument

A

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

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13
Q

reasons for atmosphere monitoring

A
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
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14
Q

Info sources

A
labels on containers
safety data sheets
HSE publications
technical info from trade assocs
accident records
health surveillance records
absence rates
staff complaints
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15
Q

stain tubes

A

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

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16
Q

advantages of stain tubes

A

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

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17
Q

disadvantages of stain tubes

A
limited shelf life
false reading from other chemicals
safe disposal issues
limited accuracy
depends on skill of operator
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18
Q

bags & canisters

A

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

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19
Q

Tyndall lamp

A

light that shows dust floating in the air

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20
Q

factors influencing health effects of dust

A

nature of the dust
particle size
exposure time
airborne concentration

21
Q

where is the breathing zone

A

300 mm in front of and around face

22
Q

dust filtration sampling system

A

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

23
Q

types of sampling head

A

protected
cyclone
cowl head

24
Q

protected head sampler

A

no problems ref orientation or wind speed

best in workplace conditions

25
cyclone head sampler
cyclones simulate nose / mouth | used for respirable dust sampling
26
cowl head sampler
for fibre sampling open faced filter cowl faces downwards
27
types of sampling pump
piston / compressed chamber rotary vane diaphragm
28
piston / compressed chamber pump
volume depends on number of pump strokes relies on manual operation cannot be used for dust sampling
29
rotary vane pump
flow rate measured with integral flow meter | sample volume = flow rate x time
30
diaphragm pump
sample volume = number of diaphragm moves
31
other pump considerations
dust explosion risk, therefore must not be source of electrical ignition battery capacity serviced regularly pump cleaning
32
filter types
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
33
filter weighing
pre-weighed and weighed again after sampling | matched weight - contains 2 filters but only one collects dust. Both weighed at lab
34
MDHS dust sampling method
``` 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 ```
35
dust measuring analysis
gravimetric physical chemical
36
gravimetric analysis
measure weight of dust collected weigh filter before and after calibrated weighing device calculate dust concentration
37
physical analysis
``` techniques inc xray fluorescence spectroscopy xray diffraction infra red atomic absorption ```
38
chemical analysis
analysis of metal dusts
39
fibre analysis
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
40
passive personal samplers
``` no pump some change colour to indicate contamination light easy to use activated charcoal to collect solvents ```
41
active personal samplers
worn by worker pump fitted to belt tube attached near to collar
42
activated charcoal tubes
absorbs vapours tube sealed with plastic caps sent off for analysis
43
sampling technique requirements
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
44
vapour analysis techniques
remove contaminant from material that absorbed it use solvent (carbon disulphide) or heat to desorbe into gas analyse vapour
45
types of vapour analysis
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
46
formula for dust concentration
weight gain in filter divided by total volume of air sampled mg / m3
47
advantages of Tyndall lamp
``` 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 ```
48
disadvantages of Tyndall lamp
provides immediate info only | does not measure particle size