transportation of dry ice on aircraft 1

[PhilLee]

I am working with the Dangerous Goods Coordinator of our small airline with the issue of dry ice. There are very broad guidlines which the aviation industry uses regarding amounts of dry ice that can be safely, however we have concerns that these values may be too high for the smaller volume of our cargo holds. We have had one incident where a package with a small amount of dry ice stored in a fairly large walk-in freezer caused an employee to pass out. Fortunately he was not working alone. We don't want something similar to occur in the air...

I need to calculate the amount of CO2 gas produced by a box of dry ice measuring 12"x12"x12".

variables
Pressure: 7,000 ft altitude (cabin pressure)
Temperature: 15deg celcius (cabin temp)
Time: 3hrs
Insulation: 0 (packed in fibre board box)

Let me know if there is additional info required...
Thanks,

 

[quark]

I again suggest (My first post-suggestion1 -30/10/2003) to actually check the rate of sublimation in the actuall conditions.

Regards,

 

[25362]

Following JOM's question, for CO2 the following threshold limit values (TLVs) have been published:

TWA 5000 ppm (volume) = 0.5%
STEL 30,000 ppm (vol.) = 3%

The STEL refers to a period of 15-min continuous exposure.

 

[25362]

As a sequel may I add that those TLVs are hardly near, and are in fact quite apart, from those required for asphyxiation by displacement of the necessary oxygen needed for breathing (Art Montemayor?).

Dry ice sublimation differs from fires in confined places in which CO₂ not only displaces oxygen by its very presence, but also by the oxygen-depleting effect of combustion.

I think Quark is right in suggesting the use of inexpensive CO₂ monitors/detectors available in the market, for concentrations above 1000 ppm, in confined spaces such as airplanes.

 

[aviat]

From FAA 25.831(b)2 Ventilation: carbon dioxide concentration must not exceed 0.5 % by volume (sea level equivalent) in compartments occupied by PAX and crew. Sea level equivalent is defined as 25deg C and 760 mm Hg pressure. From this there is no requirement for below deck cargo holds, although if you are carrying animals they should not be in same hold.

IATA allows 441 pounds per hold and even if it subliminates at the rate of 10% per 24 hours it would be 44 lbs; or 5.5 for three hours. One lb.of dry ice equals 8.3 cubic feet of carbon dioxide gas or for a 3 hour trip a total of 45.65 ft^3 of gas. This would be diluted by the required 0.55 pounds per minute of fresh air and by the pressurization leaks.

If a company were paying for airfreight to the north I would think they would ship in an insulated box to prevent loss of the ice. If they were to lose a lot of their cargo that they paid to ship, as gas, it would be an expensive.

http://www.tc.gc.ca/aviation/regserv/carac/cars/cars/525/english/525sdde.htm

http://www.dryiceinfo.com/safe.htm