Ventilation of Confined Space Training

1. Ventilation of Confined SpacesVentilation of Confined Spaces

2. Confined Space VentilationConfined Space Ventilation
Confined spaces are not normally designedConfined spaces are not normally designed
for convenient ventilationfor convenient ventilation
Must take steps to:Must take steps to:
• ensure air is breathable before enteringensure air is breathable before entering
confined spaceconfined space
• maintain acceptable air quality in the confinedmaintain acceptable air quality in the confined
space during entryspace during entry

3. Hotwork in Confined SpacesHotwork in Confined Spaces
Presents additional ventilation challengesPresents additional ventilation challenges
in confined spacesin confined spaces
Includes torch cutting, welding, brazingIncludes torch cutting, welding, brazing
and soldering, arch gougingand soldering, arch gouging

4. Hotwork in Confined SpacesHotwork in Confined Spaces
Remember… confined spaces concentrateRemember… confined spaces concentrate
hazards!hazards!
Hotwork can create atmospheric hazards inHotwork can create atmospheric hazards in
confined spaces from fumes, gasses andconfined spaces from fumes, gasses and
vaporsvapors
Effective ventilation sometimes may onlyEffective ventilation sometimes may only
be accomplished by mechanicalbe accomplished by mechanical
ventilationventilation

5. Natural Ventilation inNatural Ventilation in
Confined SpacesConfined Spaces
““Chimney Effect”Chimney Effect”
• convection process created by temperatureconvection process created by temperature
changeschanges
Occurs by sunlight heating vessel wallsOccurs by sunlight heating vessel walls
and air withinand air within
If there is an opening in bottom and top ofIf there is an opening in bottom and top of
vessel, upward draft createdvessel, upward draft created

6. Natural Ventilation ProblemsNatural Ventilation Problems
Confined spaces rarely experience uniformConfined spaces rarely experience uniform
thermal conditionsthermal conditions
Various sources of heat in confined spacesVarious sources of heat in confined spaces
• human bodieshuman bodies
• lightinglighting
• hotwork processeshotwork processes

7. Natural Ventilation ProblemsNatural Ventilation Problems
Factors such as sunlight, body heat,Factors such as sunlight, body heat,
lighting and hotwork are usually notlighting and hotwork are usually not
sufficient to move enough air to provide ansufficient to move enough air to provide an
acceptable atmosphereacceptable atmosphere

8. Overcoming Natural VentilationOvercoming Natural Ventilation
ProblemsProblems
Must establish techniques and proceduresMust establish techniques and procedures
to provide adequate ventilationto provide adequate ventilation
It is easier to workIt is easier to work withwith thanthan againstagainst
natural convection.natural convection.

9. Use of Mechanical VentilationUse of Mechanical Ventilation
Properly installed, can reduce or eliminateProperly installed, can reduce or eliminate
respiratory protection requirementsrespiratory protection requirements
Effective engineering controls usually lessEffective engineering controls usually less
dependent on worker attention thandependent on worker attention than
respiratory protectionrespiratory protection

10. 29 CFR 1910.13429 CFR 1910.134
When feasible, effective engineeringWhen feasible, effective engineering
controls must be used rather thancontrols must be used rather than
respiratorsrespirators

11. When is ventilation necessary?When is ventilation necessary?
If atmosphere:If atmosphere:
• contains insufficient oxygen or is oxygen richcontains insufficient oxygen or is oxygen rich
• contains flammable dusts or vaporscontains flammable dusts or vapors
• contains hazardous or toxic vapors, mists,contains hazardous or toxic vapors, mists,
fumes, gases, or fibersfumes, gases, or fibers

12. When is ventilation necessary?When is ventilation necessary?
If atmosphere:If atmosphere:
• is subject to activities that may generateis subject to activities that may generate
hazardous mists, vapors, fumes or gases, orhazardous mists, vapors, fumes or gases, or
may create either an oxygen deficiency ormay create either an oxygen deficiency or
oxygen excess, andoxygen excess, and
• increases heat stress on workers toincreases heat stress on workers to
unacceptable levelsunacceptable levels

13. CAUTIONSCAUTIONS
Many people resist wearing PPE, includingMany people resist wearing PPE, including
respiratory protectionrespiratory protection
Tangle of supplied air hoses in vessel withTangle of supplied air hoses in vessel with
many welders can present a hazardmany welders can present a hazard

14. Ventilation- 29 CFR 1910.252(c)Ventilation- 29 CFR 1910.252(c)
Spaces that require ventilationSpaces that require ventilation
• work space less than 16 feet highwork space less than 16 feet high
• volume less than 10,000 cubic feet per weldervolume less than 10,000 cubic feet per welder
• work areas with partitions, structural barriers,work areas with partitions, structural barriers,
or other barriers that significantly obstructor other barriers that significantly obstruct
airflowairflow

15. Ventilation- 29 CFR 1910.252Ventilation- 29 CFR 1910.252
Ventilation options:Ventilation options:
• provide at least 2000 cfm of airflow for eachprovide at least 2000 cfm of airflow for each
active welder; oractive welder; or
• provide each welder with a local exhaustprovide each welder with a local exhaust
devicedevice
– local exhaust devices must be capable oflocal exhaust devices must be capable of
maintaining a velocity of 100 fpm toward the airmaintaining a velocity of 100 fpm toward the air
intakeintake

16. Ventilation RequirementsVentilation Requirements
29 CFR 1910.252 and 29 CFR 1926.35329 CFR 1910.252 and 29 CFR 1926.353
require use of local exhaust ventilation orrequire use of local exhaust ventilation or
supplied air respiratory protection whensupplied air respiratory protection when
performing hotwork using certainperforming hotwork using certain
substancessubstances

17. Ventilation RequirementsVentilation Requirements
Fluorine compoundsFluorine compounds
ZincZinc
LeadLead
CadmiumCadmium
MercuryMercury
Beryllium (local exhaust and supplied airBeryllium (local exhaust and supplied air
respirators are required)respirators are required)

18. Ventilation RequirementsVentilation Requirements
Construction :Construction :
• chromiumchromium
• stainless steels (if using MIG processes)stainless steels (if using MIG processes)

19. Air Moving DevicesAir Moving Devices
Two types:Two types:
• FansFans
• Venturi-type eductorsVenturi-type eductors
Can be air, steam or electrically drivenCan be air, steam or electrically driven

20. EductorsEductors
Sometimes called “air horns”Sometimes called “air horns”
Air powered and rely on venturi effects toAir powered and rely on venturi effects to
move airmove air

21. Criteria for Rating Air MoversCriteria for Rating Air Movers
Free Air DeliveryFree Air Delivery
Effective Blower CapacityEffective Blower Capacity
Quantity of air and air pressure requiredQuantity of air and air pressure required
(air-driven devices)(air-driven devices)
Electrical power requirements (electricallyElectrical power requirements (electrically
driven devices)driven devices)

22. Factors Reducing PerformanceFactors Reducing Performance
Equipment components in confined spaceEquipment components in confined space
Maintenance/construction materialsMaintenance/construction materials
erected in spaceerected in space
Obstructions in make-up air manwayObstructions in make-up air manway
Insufficient number of make-up airInsufficient number of make-up air
manwaysmanways

23. Factors Reducing PerformanceFactors Reducing Performance
More restrictions to overcome = less airMore restrictions to overcome = less air
movedmoved
Air moving into space equals amount of airAir moving into space equals amount of air
leaving the spaceleaving the space

24. Air Driven Devices-Air Driven Devices-
Poor PerformancePoor Performance
Reduced pressure and volume to air drivenReduced pressure and volume to air driven
devices from multiple usersdevices from multiple users
Excessively long air hosesExcessively long air hoses

25. Increasing PerformanceIncreasing Performance
Supplemental air compressors dedicatedSupplemental air compressors dedicated
to air mover use (air driven devices)to air mover use (air driven devices)
Supplemental air compressors connectedSupplemental air compressors connected
directly to plant air systemdirectly to plant air system
Eliminate “short-circuiting” of airflowEliminate “short-circuiting” of airflow

26. Designing Ventilation SystemsDesigning Ventilation Systems
Configuration, contents and tasksConfiguration, contents and tasks
determine type of ventilationdetermine type of ventilation
• opening configurationopening configuration
• properties of expected atmospheric hazardsproperties of expected atmospheric hazards
• type of work being performedtype of work being performed

27. Electrically Driven Centrifugal FansElectrically Driven Centrifugal Fans
Designed to overcome higher staticDesigned to overcome higher static
pressurespressures
Usually heavier than air-driven equipmentUsually heavier than air-driven equipment
Can be used remotely to reduce noiseCan be used remotely to reduce noise
Due to power, can suck up debrisDue to power, can suck up debris

28. Local ExhaustLocal Exhaust
Single manway vesselsSingle manway vessels
Interior obstructions that create “deadInterior obstructions that create “dead
spots”spots”
Lack of feasible way to attach air-movingLack of feasible way to attach air-moving
devicedevice
Work with toxic metalsWork with toxic metals

29. Local ExhaustLocal Exhaust
Effective only when it captures andEffective only when it captures and
removes welding fumes and gasses at theremoves welding fumes and gasses at the
source as they are emittedsource as they are emitted
100 fpm capture velocity at the source of100 fpm capture velocity at the source of
fumes or gassesfumes or gasses

30. Local Exhaust- ConsiderationsLocal Exhaust- Considerations
Long runs reduce airflowLong runs reduce airflow
Airflow loss minimized by use of smoothAirflow loss minimized by use of smooth
ducting with large radius bendsducting with large radius bends
Run flexible ducting as straight as possibleRun flexible ducting as straight as possible
Consider using plenums for multipleConsider using plenums for multiple
welderswelders
Field test flow/personal air monitorsField test flow/personal air monitors

31. Make-up air qualityMake-up air quality
Mechanical ventilation uses surroundingMechanical ventilation uses surrounding
airair
Make sure the make-up air is not a sourceMake sure the make-up air is not a source
of airborne contaminantsof airborne contaminants