SAFETY HEALTH & WELLBEING
CARBON DIOXIDE EXPOSURE
A PhD student entered the room to retrieve some biological specimens and
began to feel dizzy. The student immediately exited the room with the
samples and then asked a colleague, a postdoctoral researcher, to come
and have a look. Briefly after entry, they exit the room suffering serious
respiratory distress. The Laboratory Superviser calls first aid officer to attend
the two students who are taken to a well-ventilated area. An ambulance was
called and the two workers are treated by paramedics
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The hazard
The risk
The Investigation
Immediate actions
Longer term corrective actions
Key safety lessons
THE HAZARD
Carbon Dioxide (CO2) is classified as a nonflammable, non-toxic gas. However serious
immediate health effects can occur if there is an
exposure at concentrations above 3% v/v in air or
30000 ppm. At higher concentrations of 8 - 15%
CO2 can cause headaches, nausea, vomiting and
lead to unconsciousness within minutes.
This room has dimensions of length 5.6 m and
width 4.8 m. Using the gas risk calculator it is
shown that a catastrophic release of one G size
cylinder will produce a high risk situation where the
resulting concentration of CO2 in air would be
greater than 3% and the concentration of oxygen in
air would be less than 18%. This would present
both a toxic and asphyxiant gas risk.
THE INVESTIGATION
THE RISK
An investigation reveals
The worst case scenario is that there is a carbon
dioxide leak at high pressure where the entire
contents of a G-Size cylinder are released quickly.
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A fast rate of release would negate any
effect of the general room ventilation.
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Approximately 16.6 m of carbon dioxide
would be released into the room from a G
size cylinder
The released carbon dioxide is heavier that
air and would not distribute evenly within
the room.
SHW_INC_INF_Carbon Dioxide Exposure_1
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CO2 is used as an emergency refrigerant
The room is small and at basement level
There is no CO2 monitoring and general
mechanical room ventilation
A similar gas controller connected to the
freezers had failed recently
CO2 is believed to be harmless by the
workers
Given that the students showed symptoms such as
dizziness and headache there is a high possibility of
dangerous carbon dioxide levels in the room. The
potential consequence could have been a fatality.
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SAFETY HEALTH & WELLBEING
IMMEDIATE ACTIONS
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A first aid officer was called to attend the two
students who were taken to a well-ventilated
area. An ambulance was called and the two
workers were treated by paramedics.
The room was isolated, the door was locked
and placarded with a ”Do Not Enter” sign to
prevent further entry into room. The room was
closed for a period of 24 hrs
An investigation of the room was completed
using a portable carbon dioxide gas monitor,
carbon dioxide levels in the room were
investigated. Normal levels of carbon dioxide
were detected, however a carbon dioxide
cylinder is empty and it appears a connection
has failed allowing the full contents of a cylinder
to leak into the room.
LONGER TERM CORRECTI VE
ACTIONS
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A fixed CO2 gas monitor is installed at a low
level within the room (CO2 is more dense than
air).
The sensor is set to alarm at two carbon dioxide
concentrations, a low level alarm, set at the
TWA (time weighted average) exposure
standard and a high level alarm set at the STEL
(short term exposure limit)
The monitor has both an audible and visible
alarm to alert users of a potential gas leak.
The CO2 concentration in the room can be
seen from a mimic display which is visible
outside of the room.
The door access is interlocked with the
monitoring and alarm system to prevent access
during alarm. Free egress is provided at all
times.
A forced ventilation system is installed into the
room to allow air change over and crossflow
within the room.
All workers are trained during an induction to
leave the room when the alarms are triggered
and not to re-enter the room until CO2 levels
are safe.
SHW_INC_INF_Carbon Dioxide Exposure_1
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A lab maintenance program is initiated to
regularly visually inspect, maintain and repair
equipment to prevent re-occurrence. All checks
and maintenance are recorded.
All staff and students are trained to recognise
the hazards and symptoms of carbon dioxide
exposure and other refrigerant gases, how they
are used, required maintenance, associated
hazards and symptoms of exposure.
A longer term plan is to have the gases
removed from the room and reticulated in from
an external store, at a lower pressure.
KEY SAFETY LESSONS
Take 5 ! when investigating a potential safety issue.
Never enter a room where you suspect there is an
asphyxiant gas leak. In this incident it was fortunate
the student immediately left the area, but a second
student should not have entered that room.
Could this incident happen to you?
Take Action Now before an incident occurs.
1. Identify compressed gas and cryogen
storage areas for potential leaks
2. Use the gas calculator to conduct an initial
risk assessment of these workspaces
3. Plan risk controls. Where necessary
mitigate the risk in these workspaces by
using higher level controls.
More information in the guideline for Working with
gases
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