Control of Welding Fume Exposures
in Shipbuilding Confined Spaces
purpose of the study
To develop and assess a ventilation training
program to reduce welding exposures in
confined spaces.
To determine if training welders can change
ventilation practices.
Motivation: excessive exposures to welding fume
 welding fume
• ultrafine particles
• hazardous components
• metals, gases, particulate matter

health risks:
• respiratory
• lung disease (COPD, Asthma)
• “metal fume fever” (galvanized)
• Cancer (SS)
• cardiovascular diseases
STUDY OVERVIEW
 Develop training concepts
 Validation of training concepts
 Develop training program
 Pre-intervention assessment
 Post intervention change
 Directions for future
Ventilation “lab” tests
After observations in shipyards, we used
a more controlled space to test which
parameters had the most effect on fume
control, such as:
•
•
•
•
Duct height
Duct proximity
Air flow
Room mixing
This helped us
develop ventilation
training guidelines.
TRAINING CONCEPTS
 Simple, pictorial
 Box model
 Exhaust placement
 Local, General
 New concept: Regional Exhaust Ventilation
 Mixing
 Exhaust vs. Supply
 Cross draft
 “Mini-fan”
 Common problems
 Short circuiting
 Dead space
ventilation training:
Basic Ventilation Concepts
ventilation training:
Practical Questions
CROSS DRAFT AND MIXING
Minifan-induced crossdraft
ventilation training:
Short circuit
ventilation training
Common Problems
verifying our recommendations
We tested our recommendations by monitoring the fume exposure by measuring
exposure before and after adjustments.
Exhaust at floor: Poor control
Exhaust high: Good Control
verifying our training principles
Geometric Mean Concentration
0
10
20
3
30
for Control and Intervention
Pre Post
Pre Post
High
Low
Pre Post
Pre Post
Near
Far
Location of Ventilation
Pre Post
Pre Post
Cross
Mix
Simple ventilation adjustments reduce worker’s exposure
INTERVENTION ASSESSMENT
 Pre- Assessment
 Questionnaire on trainees
 Monitoring in typical conditions
 Training
 In groups of up to 20 at a time
 Primarily new construction at Vigor and Dakota Creek
 Post- Assessment
 Questionnaire on same trainees
 Monitoring in typical conditions
ventilation training
About 100 workers participated in the ventilation training program at Vigor in
Seattle and Dakota Creek, in Anacortes.
•
Five sessions with
about 20 people
•
Combination of
discussion, lecture, and
ventilation problemsolving exercises
•
Training was led by an
industrial hygienist with
a background in
designing temporary
ventilation for welding in
similar situations in
refineries.
Participants filled out a survey about their knowledge and use of ventilation
before the class and again several weeks later.
Observed conditions and welding fume exposure levels
All Samples
n (%)
65 (100%)
GM (GSD)
mg/m3
2.4 (4.2)
Space Confinement
Partially Enclosed
Enclosed
Confined
5 (8%)
28 (43%)
32 (49%
1.3 (2.4)
2.2 (3.2)
2.9 (5.4)
Welding Type
SMAW
FCAW (Dual Shield)
FCAW (Inner Shield)
Oxyacetylene
5 (8%)
49 (75%)
5 (8%)
6 (9%)
0.8 (4.5)
3.2 (3.6)
3.7 (4.9)
0.4 (2.9)
Ventilation Type
No ventilation
Supply blowers
Exhaust blowers
Supply & exhaust blowers
19 (29%)
19 (29%)
25 (38%)
2 (3%)
2.3 (4.4)
4.3 (4.2)
1.8 (3.7)
0.6 (7.2)
n (%)
GM (GSD)
mg/m3
Exhaust Vent Proximity
Local
Regional
General
2 (7%)
6 (22%)
19 (70%)
1.1 (47.1)
2.1 (1.9)
1.6 (3.5)
Deadspace
No
Yes
31 (48%)
34 (52%)
2.4 (3.8)
2.4 (4.7)
Crossdraft
No
Yes
55 (85%)
10 (15%)
2.7 (4.5)
1.4 (2.6)
Respirator Used
No
Yes
11 (17%)
54 (83%)
0.9 (3.3)
2.9 (4.1)
QUESTIONNAIRE RESULTS
CHANGE IN SCORE ~ 1 MONTH POST TRAINING
Worthwhile setting up for short job
Too much work for any length job.
Takes too much time to set up
Confidence in my ability to decide what vent works best
Confidence in my ability to set up ventilation
Properly used vents can reduce my exposure
Properly used vents will increase the comfort and visibility
Properly used vents will reduce exposures of others
n
Post-Pre
improvement
SE
71
0.11
0.13
70
0.17
0.14
69
0
0.13
70
0.17
0.1
71
0.1
0.83
71
-0.01
0.08
71
-0.28
0.09
71
-0.03
0.07
Mean score based on a 1 to 5 scale
QUESTIONNAIRE RESULTS
CHANGE IN % CORRECT ~ 1 MONTH POST TRAINING
Pre-training
% correct
Post-training Change in
% correct
% correct
You may need a respirator even when using vents
100
100
0
When exhausting the length of duct does not matter
86
85
-1
Weld quality is always reduced if air is moving past you
78
69
-9
Welding smoke is heavy and settles
72
75
3
The number of blowers needed depends on number of welders
69
79
10**
How many blowers are needed to ventilate 9x9x9 ft space?
56
71
15**
Which of the images shows short-circuiting?
22
18
-4
Which type of exhaust ventilation is practical and effective?
25
34
9
What advantage does blowing have over exhausting?
60
56
-4
** McNemar’s test of proportions, p<0.05
STUDY RESULTS AND CONCLUSION
 Shipyard environment is very challenging
 For environmental control
 For conducting research
 Ventilation CAN be set up in confined spaces to significantly
reduce exposure to welders
 Sufficient fresh air supply
 Strategically placed for fume removal
 Dissipation where appropriate
 But it is not being ef fectively used in many conditions
 A single training for welders is NOT suf ficient to change
practices
 Many barriers and organizational constraints which training alone
cannot overcome
Recommendations
 Continue to develop expertise within welding and support trades to increase
effectiveness of ventilation
 Develop system to identify adequacy of ventilation during work
 Continue supporting use of respirators as needed
Next steps:
 Further analysis
 Dissemination of results and training materials through:


Scientific journals
Research group website: https://blogs.uw.edu/uwseixas/
 Suggestions for additional dissemination?
THANK YOU!
We greatly appreciate the participation and support from:
•
•
•
•
•
Puget Sound Shipbuilders Association
Vigor Shipyards
Dakota Creek
Foss Maritime
Lake Union Dry Dock
• Contributors:
•
•
•
Faculty: Noah Seixas, Hendrika Meischke, Mike Yost, Lianne Sheppard
Staff: Chris Warner, Rick Neitzel, Marc Beaudreau, Bert Stover, Gerry Croteau
Students: Jane Pouzou, Jeff Walls, Lea Duffin, Eddie Kasner
air monitoring and observations
We measured how well different ventilation setups worked in
real situations by observing and monitoring the fume levels in
the spaces where welders were working.
Hundreds of assessments of ventilation
were made at Vigor, Dakota Creek, Foss,
and Lake Union Dry Dock.
common ventilation problems
 “Short-circuiting” of the air
 Excessive bends or kinks in duct
 Inadequate equipment for space and
amount of welding (many spaces that
needed multiple blowers only had one)
 Poor placement of the duct
• Too far from the fume
• Too low to the ground
a preliminary study in other shipyards showed:
 Use of ventilation:
• 3% used local exhaust ventilation
• 29% used dilution ventilation (either
exhaust or supply)
• 68% did not use LEV or DV
 Use of a respirator: 41%
 Exceedance of the 5 mg/m 3 8-hour
TWA PEL:
• Overall: 82%
• Confined spaces: 94%
• Enclosed spaces: 70%
• Spaces with dilution ventilation: 31%
• Spaces with local exhaust
ventilation: 100%