1
Objectives
 Describe the ionization process
 Describe the various types of ionization detection

devices
 Identify the ...
Photoionization Dectectors
 The most common

detector of general toxic
risk is the
photoionization detector
 PID are ver...
Photoionization Dectectors
 Can detect organic and some inorganic gases.
 Ammonia, Arsine, Phosphine, Hydrogen Sulfide,
...
Photoionization Detectors (PID)
 May be built into a multi-gas meter
 Advantage – sensitivity



PID starts to read at...
Photoionization
 PID uses ultraviolet lamp to ionize gas
 Gas sample has various molecules

 Neutrons (neutral), proton...
Photoionization
 In order to be read by a PID,








the vapor or gas to be
sampled it must be able to be
ionized ...
Photoionization

8
Photoionization
 Know the chemical you are dealing with to determine

quantity of material present
 Compare readings you...
Photoionization
 What is a toxic reading

As a rule of thumb for an
occupancy that has
chemicals is use.
 50 ppm may be ...
Problems with PIDs
 Humidity affects this in 2-ways
 If you have a dirty lamp and sensing area the water vapor
may creat...
Problems with PIDs
 Higher levels of Methane (Natural gas, Swamp gas, landfill gas)

May suppress some of the ionization ...
Summary
 Understanding use of ionization devices can detect

potentially toxic environments
 Understanding how these dev...
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Module 4 ionzing detection units, american fork fire rescue

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Module 4 ionzing detection units, american fork fire rescue

  1. 1. 1
  2. 2. Objectives  Describe the ionization process  Describe the various types of ionization detection devices  Identify the uses for ionization detection devices  Compare types of ionization detection types and use in emergency response 2
  3. 3. Photoionization Dectectors  The most common detector of general toxic risk is the photoionization detector  PID are very common in the scientific community  Several methods to provide the ionizing energy through ionization  PID uses an ultraviolet lamp.  The method of ionization may vary but the end results are the same  Vapor is separated and the resulting change in electrical activity is measured against a know gas.  PID detects a variety of gases.  LEL sensor does not detect low enough to protect responders against toxic risk. 3
  4. 4. Photoionization Dectectors  Can detect organic and some inorganic gases.  Ammonia, Arsine, Phosphine, Hydrogen Sulfide, Bromine, Iodine.  Has the ability to detect a wide variety of gases in small amounts  Dose not indicate what the material is  It justifies that something is in the air 4
  5. 5. Photoionization Detectors (PID)  May be built into a multi-gas meter  Advantage – sensitivity   PID starts to read at 0.1 ppm to 2,000 or 10,000 ppm LEL typically will start to read at 50 ppm  RAE systems has PPB RAE  Can detect down to 1 PPB  LEL sensor identifies flammability issues  PID determines toxic risk – PEL less than 500 ppm are considered toxic 5
  6. 6. Photoionization  PID uses ultraviolet lamp to ionize gas  Gas sample has various molecules  Neutrons (neutral), protons (positive), electrons (negative)  Ionization–electron is removed resulting in a charged particle (ion)  PID detects change and makes reading 6
  7. 7. Photoionization  In order to be read by a PID,      the vapor or gas to be sampled it must be able to be ionized (Ionization potential) Measurement of an IP is electron volts (eV) Found in the NIOSH pocket guide UV lamps 9.8 eV, 10.2 eV 10.6 eV most common 11.7 eV, 13.0 eV 7
  8. 8. Photoionization 8
  9. 9. Photoionization  Know the chemical you are dealing with to determine quantity of material present  Compare readings you get with the PEL or IDLH to determine your safety  PID has correction factors as well  Most PIDs are calibrated to isobutylene 9
  10. 10. Photoionization  What is a toxic reading As a rule of thumb for an occupancy that has chemicals is use.  50 ppm may be acceptable  Small: 5-10 ppm could be harmful or safe depending on the environment  Large: 1800 could be harmful or safe depending on the environment  Reading only indicates that could be something potentially toxic in the air.  Best to use PID for a variety of situations to get used to the types of reading that can be anticipated. 10
  11. 11. Problems with PIDs  Humidity affects this in 2-ways  If you have a dirty lamp and sensing area the water vapor may create a short which will cause a meter reading.  Is a quenching problem, if there is humidity in the area of the lamp, much as fog absorbs the energy of headlights? The meter reads  Lamps are affected by dirt and dust and require 99 cleaning  Diesel exhaust and other particulate matter. Like mown grass or cement dust $595  Salt water or hard water environments may affect the lamp as well 11
  12. 12. Problems with PIDs  Higher levels of Methane (Natural gas, Swamp gas, landfill gas) May suppress some of the ionization potential of the lamp.  Use an LEL monitor to read LEL PID will not read methane (IP 13.0)  PID cannot separate out gas mixtures.  Mixtures can present an identification problem   Some PID requires at least 10 percent oxygen to be present.  RAE systems PID do not require any oxygen to function. 12
  13. 13. Summary  Understanding use of ionization devices can detect potentially toxic environments  Understanding how these devices function can assist in the selection process during an emergency response 13

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