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Practical Considerations For Air Monitoring With Emphasis On Direct Reading Real Time Monitors

Practical Considerations For Air Monitoring With Emphasis On Direct Reading Real Time Monitors

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Practical Considerations For Air Monitoring With Emphasis On Direct Reading Real Time Monitors

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  1. Practical Considerations For Air Monitoring With Emphasis On Direct Reading Real Time Monitors Occupational Hygiene Association of Ontario Spring Symposium By: Jamie Prince B.Sc, OHST, ROHT General Motors of Canada Limited

  2. OUTLINE • What Can Be Measured • Sampling Strategies • Types of Sampling Equipment • Examples of Real Time Monitors • Advantages/Disadvantages of Real Time Air Monitoring • Real Time Air Monitoring Examples • Conclusions

  3. PHYSICAL/CHEMICALSTATES • solids: dust, fibres, fume, smoke • liquids: mist, aerosols • gases: vapours remember: gas solid liquid

  4. 7 TYPES OF CONTAMINANTS • Dusts- airborne solid particles ranging in size from 0.1 to 25 microns. Particles 5 microns and larger don’t usually remain airborne to present an inhalation hazard. • Fumes- material from a volatized solid condenses in cool air. Size of the particulate formed are less than 1 micron in diameter. • Smoke- from incomplete combustion of carbon containing materials, its made up of carbon or soot particles. Can vary in size.

  5. 7 TYPES OF CONTAMINANTS • Aerosols- liquid droplets or solid particles, fine enough to remain dispersed in air for a prolonged period. • Mists- liquid droplets suspended in the atmosphere. • Gases- are “formless fluids” that expand to fill the space or enclosure in which they are confined. • Vapours- are the volatile form of substances that are usually in the liquid or solid state at room temperature and pressure.

  6. PHYSICAL/CHEMICAL STATES • size: respirable (less than 10 μm) fibres (length & diameter) • chemical charge (CrIII or CrVI) • solubility (Ni) • crystal structure (silica, talc) • fibrous or non-fibrous • polar/non polar

  7. MIXTURES • decomposition products (smoke, etc.) often have thousands of components • sometimes “marker” substances measured (like CO) • if a “marker” is used, the TWAEV for the marker substance is not applicable! • can be sampled as a group (e.g. VOC’s), but usually no TWAEV

  8. MIXTURES • Measuring each of the thousands of constituents in decomposition products would be a chemist’s nightmare • almost all of the constituents will be well below individual TWAEV’s • even summing the TWAEV’s seldom exceeds summed TWAEV criteria • Combinations: • Vapour condensing on particles • vapour absorbed by liquid aerosols • liquid evaporating from aerosol/particulate

  9. SO YOU WANT TO SAMPLE? Then answer the 5 W’s and 3 H’s: • Why? • What? • Who? • When? • Where? • How? • How many? • How long?

  10. SAMPLING STRATEGIESWHY? • Reactive Sampling, Source Identification -Employee Concerns: What’s causing the complaints/symptoms • Compliance Sampling, New Process, DSR • Proactive Sampling • Engineering Control Verification

  11. ALTERNATIVES TO SAMPLING • Eliminate the source • Add engineering controls • Use odour and irritation thresholds • Hazard mapping, use employee experiences • Computer modelling

  12. EXPOSURE CONTINUUM source > path > exposure > uptake > target Try to move as far to the left of the continuum as possible (prevention!) • Source: substitution, enclosure • Path: ventilation evaluation, work practices • Exposure: IH measurements • Uptake: symptoms, blood/urine samples • Target: clinical tests, diagnosis

  13. SAMPLING STRATEGIESWHAT? • Type: bulk, area, personal • Time: short term (CEV, STEV), long term (TWAEV), sequential, grab (series) • Method: “quick and dirty” (colourimetric), direct reading real time, official (NIOSH etc) • Conditions: worst case, random (unbiased), staged (simulated), regular work shift. • Number: “one shot”, statistically representative, cumulative exposures

  14. WHO WHEN WHERE? What workplace variables cause exposures to go up or down? • weather (season, temp, humidity, wind) • doors & windows, cross drafts • shift, production schedules, rates • ventilation in other areas of plant • housekeeping, traffic, activity levels • individual work practices, man cooling fans

  15. SAMPLING CONDITIONS • make sure important variables are addressed in strategy • keep records of conditions during sampling • start & finish times • production levels • ventilation (doors, windows, local & general) • workers’ opinion if sampling period is representative of better than average, normal, worse than normal conditions

  16. HOW?TYPES OF SAMPLING EQUIPMENT • Colourimetric (Draeger tubes, dositubes) • Passive Absorption Badges: Organic Vapours, formaldehyde, other gases and vapours • Pumps: • filter cassettes (with or without cyclones or impacters) for particulates, aerosols and fibers • sorbent tubes, (charcoal, silica gel, specialized) for gases and vapours. • Liquid samplers (impingers) for vapours, particulates, aerosols

  17. TYPES OF REAL TIME AIR MONITORS • Particulates • Total particulates/aerosols (data-logging): DataRam, Dust Trak • Fibers: FAM (Fibrous Aerosol Monitor) asbestos • Gases/Vapours • FID and PID (data-logging) for organic compounds • Inorganic gases and vapours, CO, CO2, mercury, H2S • Paper Tape for isocyanates • Lead Niton X-ray fluorescence • Indoor Air Quality multi-function monitors

  18. HOW MANY? How Many Samples Do You Need To Take? • Compliance sampling needs a large number of representative samples over a long period of time • use traditional sampling methods • Worst case sampling may require only a few samples over a short period • direct reading or real time may be required • Type of hazard may determine how many and for how long • peak exposures, length of peaks, short term acute hazards, does it come and go

  19. HOW LONG? • Lowest detectable quantity • Don’t overload sample media • Short sample period for acute hazards • Chronic hazard may need full shift • Peaks need data-logging, real time direct reading or short term sequential samples • IDLH for confined space needs immediate answer • Leak detection needs direct reading

  20. DISADVANTAGES OF LONG TERM SAMPLING • Analysis and Feedback time too long, chance of exposing employees to hazardous levels • Inability to answer employee concerns, continued refusal to work, loss of production • Inability to Determine STEL and Ceiling Values, ie. short term maintenance jobs • 90% of all long term samples were less than 10% of any EEG, however employees continued to complain, especially of irritation • Ineffective use of Hygienist’s time

  21. ADVANTAGES OF REAL TIME • Instant feedback of exposure levels to hygienist and employees, ease of mind • Employee trust, can see exposure on meter • Ability to determine time vs concentration with data-logging instruments • Ability to determine STEL and Ceiling Values • Quick determination of how changes to process or engineering controls affect employee exposures • More efficient use of hygienist’s time

  22. DISADVANTAGES OF REAL TIME AIR MONITORS • Specificity of monitor • Interpretation of results, employee misunderstanding • Interferences, CO, TOHC’s , Water Vapour • Method may not be accepted by Government • Difficult or unable to Calibrate • Assuming dust monitor detects all particle sizes equally well • Cannot usually be used for compliance sampling, lead, isocyanates, silica, asbestos • Accuracy


  24. SEALER REMOVAL SOLVENT INSTRUMENT- CENTURY SYSTEMS OVA • Sealer removal from car in open area • which solvent had lowest exposure levels • FP and VP not useful • solvent 1- 35-40 ppm peaks TWA 100 ppm • solvent 2--50-60 ppm peaks TWA 100 ppm • solvent 3--35-40 ppm peaks TWA 100 ppm • solvent 4--20-30 ppm peaks TWA 100 ppm • solvent 5---85-100 ppm peaks TWA 400 ppm • Solvent 4 or 5 recommended • Solvent 4 chosen because of higher FP

  25. FLAT TOP CO INSTRUMENT- DRAEGER CO DATALOGGER • CO buildup suspected for new driving and parking procedures on flat top conveyor • CO levels data-logged in various areas ventilation on and off • CO levels data-logged while different procedures were used for idling cars while parked • Determined that new procedures did increase CO to hazardous levels in one area. • Immediate ventilation system changes reduced maximum CO levels to non hazardous levels

  26. COAST CLUTCH BLOWOFF INSTRUMENT-DATARAM AEROSOL MONITOR • Using compressed air to blow off and clean Transmission parts. Does ventilated box and lower air pressure reduce exposures. • Total particulates data-logged while blowing off parts in general work area • TP’s data-logged with part held in ventilated box • Determined box increased exposures since exhaust in box too low, and blow back • Lower air pressure decreased exposures

  27. BLACK PRIME INSTRUMENT-CENTURY SYSTEMS OVA • Black prime with MEK applied to window openings on ventilated ramp, employees complain of irritation and odours • How did casablanca fan speed and application method affect exposures • MEK levels taken in BZ and general area with fans on high 3X higher than fans on low • MEK peak levels taken In BZ while leaning over applied prime 4X higher than when furthest part of window was primed first • Set fans to low speed, disabled rheostats • Rec’d not to lean over applied prime

  28. PAINT SPRAYING INSTRUMENT- CENTURY SYSTEMS OVA • Employees paint spraying rear of vehicle • Long term test showed paint solvent exposures <5 ppm, but employees continued to complain of irritation and odours • sampled BZ while spraying across from each other, found peaks of 200 ppm TOHC from overspray • sampled BZ while staggering their spraying, found peaks below 10 ppm • Recommended that paint sprayers in all booths stagger their paint spraying

  29. METAL WORKING FLUIDS INSTRUMENT- MINIRAM AEROSOL MONITOR • Employees working on machining line complaining of irritation, all equipment ventilated • Miniram used to survey BZ and general work area • Levels in area rose slowly as machining progressed • followed plume of mist back to one faulty filter • after filter repaired, levels remained low • Recommended preventative maintenance on filters of ventilation equipment

  30. METAL WORKING FLUIDS INSTRUMENT(S)- DATARAM AEROSOL MONITOR & TSI DUSTRAC • Total Particulate Levels Required to Determine Need For Engineering Controls • Total Particulate Mapping of Component Manufacturing Plants on a 6mX 6m Grid. • Results plotted on an Excel Spreadsheet. Chart of Exposure Levels (Contour) Printed on Overhead. • Contour Chart Overlaid on Plant Layout. • Areas of Higher Exposure Targeted for Improvement • Engineering Controls installed • Plant is Remapped to Determine Improvement

  31. Conclusions • Is sampling necessary, can the problem be solved another way? • Ensure your sampling strategy is right. • Real time air monitoring benefits include: • ability to determine patterns of exposure • ability to quickly evaluate engineering or process control changes • reasonably determine potential of exposure to cause adverse health effects • dollar savings from reduction of lab analysis and hygienist’s time being used more effectively