Transcript CO on loading dock

Carbon Monoxide office exposure
during construction
John S. Morawetz
ICWUC Center for Worker
Health and Safety Education
[email protected]
513-621-8882
Summary
A propane powered welding generator was used for construction purposes at a building that is occupied by a
Training Center in Cincinnati, Ohio. Through the prompt use of a direct reading carbon monoxide (CO)
meter, the staff was able to remove the source of the exposure and take rapid action to lower exposures to the
staff. Exposure levels were recorded at various locations that demonstrate a wide variability of CO levels,
some of which persisted for hours.
Background
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Cincinnati, Ohio: Downtown 14 story office building
ICWUC Center a tenant since 1988
Building sold in January, 2011
Landlord is converting floors 4 to 14 from offices to apartments
Basic Office Layout
Loading Dock and Alley
There was a history of diesel trucks
in alley adjacent to loading dock.
In the 1990s, Center staff had notified the previous building
management about diesel emissions from the loading dock being
noticeable inside the Center office space. This sign was
subsequently posted in the alley adjacent to the loading dock.
Carbon Monoxide (CO)
CO is a colorless, odorless and very toxic gas that is a common byproduct of incomplete
combustion and improperly vented combustion devices. Unintentional and non–firerelated CO poisoning is responsible for more than 230,000 emergency department visits,
22,000 hospitalizations and approximately 450 deaths annually in the United States
although rates appear to be falling recently. At lower levels of exposure, CO causes mild
effects that are often mistaken for the flu (headaches, dizziness, disorientation, nausea and
fatigue).
January 5, 2012
Propane powered generator was needed for welding work. It was put on the loading dock with the door lowered
but no venting. The temperature was app 23 over night; 30 during the AM.
With Loading door open
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Door closed and location of generator
Staff observed the generator on loading dock
Staff retrieved CO direct reading instrument (GasAlertMicroClip XT; 4 gas detectors); range 0 – 500 ppm
OSHA PEL 50 ppm -8-hour time-weighted average.
NIOSH’s REL 35 ppm - 8-hour TWA and 200 ppm as a ceiling.
ACGIH TLV 25 ppm - 8-hour workday.
Carbon Monoxide (CO) levels
10:45 AM
Loading dock – 100 to 115 ppm
10:47 AM
Generator turned off and moved to
alley
10:50 AM
15 ppm – Instructor #1 office
25-30 ppm in Classroom
1 PM CO levels persisted
15 ppm – Instructor #1, 2 offices
Management notified and expected appropriate steps to be
taken to minimize/eliminate future exposures.
January 6, 2012
Generator on loading dock with door lowered
Vented through flex hose under loading dock door
CO on loading dock – 27 ppm at 11 AM
Flex hose location
Carbon Monoxide (CO) levels
11:00 AM
Loading dock – 27 ppm
Reception area – 15 ppm
11:05 AM
10-15 ppm – Instructor #1, #2 office
25 ppm in Classroom
Carbon Monoxide (CO) levels
11:15 AM
35-38 ppm around elevators OUTSIDE
Office area
This demonstrates the ability of CO to
migrate to other areas. The elevators are
outside the Center area but one level below
ground as seen below.
11:18 AM
Generator turned off and moved to alley
Exterior Office door opened
11:35 AM
0 ppm - Reception area
View from Center entrance along the long
side of office area.
Entrance is just above basement level but
one level below ground at the classroom
and rear elevators area.
Epilogue
March 6, 2012
Staff noticed welding materials entering building
Direct Reading unit turned on
2nd floor: 27 ppm; recalibration indicator on
It is discovered that generator is now operating in a construction room
INSIDE the building on the first floor
First Floor Layout
10:15 AM - Generator turned off
Basement level monitored
10:45 - all 20 ppm
Reception area, Elevator, Kitchen
Hall
Second floor – 10:50 am
Office #3 – 11 ppm
Office #4 – 22 ppm
Hall – 22 ppm
11 AM
Generator moved to street with cables
into the building.
Conclusions
Exposures reduced but still significant
Significant exposures to a well known hazard continues to exist and OSHA
standards may have been exceeded.
CO danger from companies using propane generators not well addressed.
CO can rapidly spread throughout office buildings.