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Physical Factors
October 10, 2016
Physical Factors – Noise, Vibrations
November 21, 2016
Physical factors – Non-ionising Radiation, Lasers
November 28, 2016
Physical factors – Ionising Radiation, Thermal comfort
Distribution of physical factors
A. Waves
1) Mechanical waves
a) noise - periodic changes of pressure in air layers
b) vibrations - oscillatory motion of an elastic environment about a fixed
point
Distribution of physical factors
2) Electromagnetic waves
a) non ionising radiation – lower frequency range
• radio waves (broadcasting, television)
• microwaves (generators, warming ovens)
• radar waves (radio locators)
• infrared radiation (thermal radiation)
• visible light (red - violet)
• ultraviolet radiation (A, B, C)
b) ionising radiation (alpha, beta, gamma, X-rays) – high frequency range
Electromagnetic Spectrum
„Spectre“ od Tatoute and Phrood – neznámý. Licencováno pod CC BY-SA 3.0 via Wikimedia Commons -http://commons.wikimedia.org/wiki/File:Spectre.svg#/media/File:Spectre.svg
Distribution of physical factors
B. Thermal Comfort
Environmental factors
1) Air temperature
2) Air humidity
3) Speed of air flow
4) Intensity of heat radiation
Individual factors
1) Activity
2) Thermal resistance of clothes
Ionising RadiationPhysical substance
Main sources of ionising radiation exposure in peace
1) Nature background
2) Medical exposure (X-ray examination, radio-therapy)
3) Nuclear energetics and liquidation of radio-active waste
4) Mining of radio-nuclides
5) Objects of common consumption (very old TV and computer tubes, some
phosphorescent materials)
Ionising RadiationCommon principles of health protection
1) Principle of justification – activity involving irradiation must be justified
(indication)
2) Principle of optimalization – the radiation must be as low as reasonably
attainable
3) Principle of non-exceeding the limits
4) Principle of source protection – physical protection of the source against
misuse by other person, and safeguarding its technical safety.
Ionising RadiationMethods of optimisation X-ray diagnostic and therapy
Technical arrangement
Limitation of entry field, shielding of non-irradiation body parts
Sufficient sensibly film materials and correct combination with folio make shorter exposure time, today also computer transmission without film use
Limitation of skiascopic examinations
Organisational arrangement
Good record-keeping of X-ray examination
Good access to X-ray medical report
Collaboration radiologists from different wards in hospitals
High caution by examinations of sexual organs
Ionising RadiationTypes of radio-nuclides
Sealed source of ionising radiation
A type of radio-nuclide, whose arrangement eliminate a possibility of elusion
of radioactive materials for anticipated conditions
cobalt bomb (complete arrangement)
Opened radio-nuclide
A type of radio-nuclide, which don’t answer to qualification of a sealed
source of ionizing radiation
Various radioisotopes (radiopharmaceutical materials)
Ionising RadiationBasic quantities in ionising radiation problems
Absorbed dose (D)
Energy absorbed per unit mass.
Its unit is the joule per kilogram, which is given a special name Gray: (Gy = J/kg)
Equivalent dose (H)
Absorbed dose (D) correct by special factor according to relative biological
effectiveness of radiation.
The unit is also joule per kilogram, with a special name Sievert: (Sv = J/kg)
Activity
Mean number of radioactive decays per unit time.
The unit s-1 has a special denotation Becquerel: (1Bq = s-1)
Ionising RadiationPrinciples of protection
Against (ionising) radiation
1) Distance – with square of distance is lowering absorbed energy of radiation
2) Shielding – materials containing lead, plasters with barium carbonate
3) Time – shorten of exposure time
Against radioactivity contamination (Opened radio-nuclides)
1) Work with liquid substances, no with powder materials (danger of inhaling or
spilling)
2) Work in small space – protection box, fume chamber
3) Work with a minimum necessary quantity of substance
Ionising RadiationMonitoring and prevention
(Radio) Active patient
A patient, which received radio-nuclide mostly in diagnostically order
Individual monitoring of persons in external irradiation risk
1) Personal dosimeter
2) Finger thermo-luminous dosimeter (work in protection box)
Individual monitoring of persons in inner contamination risk
1) Direct – External measuring by whole-body computer
2) Indirect – Excretion analysis (blood picture, haemato-crite, chromosomal
aberrations of lymphocytes, immunological indicators)
Ionising RadiationHealth contra-indications to work in external
irradiation risk
1) Pregnancy or lactation
2) Age lower than 18 years
3) Blood diseases and bleed diseases
4) Skin carcinomas and skin pre-carcinomas
5) Ovarian insufficiency
6) Vascular disorders
7) Organic disorders of nervous apparatus
8) More serious neurosis
9) Blood pressure exceeded normal limits
10)Skin disorders
11)Cataract
Thermal ComfortFactors determining temperature comfort of humans
Environmental factors
1) Air temperature
2) Air humidity
3) Speed of air flow
4) Intensity of heat radiation
Thermal ComfortFactors determining temperature comfort of humans
Individual factors - objective
1) Activity - transformation of chemical energy to thermal energy
2) Clothing insulation between an organism and environment - thermal
resistance of clothes
Individual factors - subjective
1) Adaptation and thermoregulation mechanisms (sensitive - resistant)
2) Health state (healthy - sick)
3) Mental conditions (comfort - stress)
4) Conditions of an organism (sleepy, rest, exhausted, satiety, hungry, etc.)
Thermal ComfortThermoregulation mechanisms of an organism
Convection - an exchange between warm air layers in clothes and
neighbouring cooler air
Conduction - take away of warmth to cooler areas
Heat radiation - infrared radiation
Evaporation - evaporation by perspiration from a body surface
Thermal ComfortMeasured quantities
Temperature
One of the important parameters to evaluate thermal comfort;
The recommended range for internal air temperature in apartment houses is
between 19 and 23 °C (grades of Celsius) in winter, and less than 27 °C
(grades of Celsius) in summer.
For temperature measuring we use any type of thermometers;
Thermal ComfortMeasured quantities
Air humidity
Absolute humidity - concentration of water vapours in air [g.m-3]
Relative humidity - a ratio between actual and maximum quantity of water
vapour by given temperature [%]
Thermal ComfortAir humidity
Hair hygrometer and thermohygrograf
Thermal ComfortAir humidity
Digital hygrometre and Psychrometer
Thermal ComfortAir humidity
The psychrometer compose of
a) normal thermometer
b) thermometer with a muslin sock, soaked in distilled water.
Both thermometers are aerated with a fan.
The air streaming from the fan evaporates water from the wet sock, and therefore
damp thermometer shows a lower temperature than the dry one.
The psychrometric difference is indirectly
proportional to the air humidity.
Thermal ComfortMeasured quantities
Air flow
Air flow in outdoor environment
(the wind) we measure by
different types of anemometers
Thermal ComfortAir flow
Low velocity random air movements
can be measured by Kata-thermometer
1) the cartridge we warm up in warm water
2) Then the cartridge fall is besides air temperature given also speed of air streaming.
3) The higher is a speed of air streaming the shorter is the time of cartridge fall.
Thermal ComfortMeasured quantities
Heat radiation
The principle of heat radiation is infrared energy exchange between a
human body and surrounding surfaces.
We find a serious radiate load in hot workplaces (glassworks, blast furnaces)
Thermal ComfortHeat Radiation
Heat radiation is measured by a
Globe thermometer. Globe
thermometer is a hollow metal globe
covered by a layer of polyurethane
foam, with a mercury thermometer
inside.
Its construction enables concentrate
IR radiation from surrounding areas
(walls, floor and ceiling).
Thermal ComfortMeasured quantities
Energy output
Net (clear) issue
measuring of heart activity (Holter apparatus)
orientation estimate: pulse rate, or spreadsheet method
A basal metabolism
an energetic value of basal metabolism depends on sex and falls with age (graphic finding)
Total (gross) energy output
nett (clear) energy issue + basal metabolism
Thermal ComfortMeasured quantities
Thermal resistance of clothes
Thermal resistance of clothes depends
on:
1) Number of clothes layers
2) Speed of air flow
The higher is the number of cloth layers,
the higher is number of thermal
insulation layers among these layers.
We can see a strongly decreasing of
protective ability of clothes against cold
by increase of air streaming speed.
Thermal ComfortEvaluation
Optimal thermal load - for apartment houses or for workplaces where only
moderately heavy work is performed. The table takes into consideration
winter and summer periods and combines all thermal comfort factors
except humidity. In these places humidity isn’t in most cases serious
problem.
Long-term feasible thermal load - for work places where heavier work is
performed (energy load, temperature). The graphs combine all thermal
comfort factors.
Short-term feasible thermal load - for work places with heaviest work (high
energy load, high temperature). They combine all thermal comfort factors.
They also include a time limit for non-interrupted work in such heavy
conditions.
