If you wish to ship [
food, medicine, or biological materials, etc.] by air, for sure you will use
dry ice as a cooling product and you must declare the net quantity per each
package and write a note on the air way bill.
Carriage of dry-ice is
limited under the Dangerous Goods Regulations [ ICAO, FAA ,EATC, IATA ,CAA Etc.
] and each airline may have dry ice limitation on aircrafts.
In the above small introduction, you understand " Why solid carbon dioxide is called dry ice?". In this article I am going to give you a short summary about it. At the end of this summary, you will enrich your knowledge about the effect of Dry Ice on human health.
Why Dry Ice Is Dangerous?
Sublimated dry ice will
produce gaseous carbon dioxide[ CO2 gas ]. Carbon dioxide is, of course, a
natural component of human, animal, and plant metabolism and is a normal
constituent of the atmosphere, which contains approximately 390
ppm of carbon dioxide.
Exposure to high
concentrations of carbon dioxide gas, above 5%, can cause asphyxiation. Since
carbon dioxide is much denser than air, it will settle in low spaces over time,
and entry into closed area.
However, there are
other health considerations as well. The concentration
of carbon dioxide gas in the lungs is an important factor in regulating
human respiration, and therefore concentrations lower than those required for
asphyxiation are harmful. If the concentration of carbon dioxide is
1% (10,000 ppm), a healthy person will experience:
Why?
As the
concentration builds, the heart rate and breathing rate increase. At 2%, these
healthy persons tend to feel heaviness in the chest and experience
deeper respirations. At 3%, the breathing rate and heart rate double, and
double again as the concentration reaches 5%. At concentrations above 5%,
some persons can become unconscious and die if not removed from the
high carbon dioxide concentration.
What about persons doing strenuous activities?
Persons doing such
strenuous activities such as loading or unloading baggage or cargo, the effects
will occur at lower carbon dioxide concentrations.
Is there more dangerous properties for dry ice?
A- Dry Ice Frostbite
Dry ice is extremely cold! Skin contact kills the cells, giving you a dry ice burn. It only takes a couple of seconds to get burned.
B- Risk of the dry ice container rupturing
In one of my DGR training classes, I listened to a senior cabin crew who told me a real story about dry-ice, during the flight they heard a loud explosion in the cabin; he went to passenger cabin to check what happened, he asked a passenger, he found that he was carrying dry ice in a closed container [ to keep his medicine cold ]and the container was placed on the overhead bin; due to the type of the container; it does not let the release of carbon dioxide gas, for this reason, the gas was built-up in the container, and thus was the cause of rupturing of the container with small sound of explosion.
Dry ice is not flammable or explosive, but it exerts pressure as it changes from solid dry ice to gaseous carbon dioxide. If dry ice is placed in a sealed container, there is a risk of the container rupturing.
Now, I am sure that you will agree with the fact that Dry Ice is dangerous.
Additional Sources of Carbon Dioxide in The Air Inside an Aircraft
Beside dry ice carried on
aircrafts by airline [ food cooling], passengers and in cargo holds [ as
cargo]. There are additional four sources of carbon dioxide
can contribute to the concentration of carbon dioxide in
the air inside an aircraft:
- The carbon dioxide already presence in
fresh air from outside.
- Carbon dioxide produced from human metabolism by
the crew and the passengers, if present.
- Carbon dioxide produced from metabolism by any
animal presents on the aircraft.
- Carbon dioxide produced by the sublimation of dry ice.
Dry Ice Limits for Aircrafts
I will give you
a summary of this:
1- FAA
The carbon dioxide
concentration limit for aircraft of 5,000 volume ppm. And limited
volume, % is 0.5. [ volume of equipped cabin or cargo compartment]
2- Airbus
As aircraft manufacturer, Airbus on
its guidance, dry ice limit on aircraft is the sole responsibility of the
operator[airline]. while the maximum concentration in the cargo holds
not exceed 5,000 ppm, and it recommends using 200 kg of dry ice per cargo
compartment as a general limit.
3- Boeing
On the side of Boeing,
in its presentation has an equation for the calculation
of acceptable dry ice loads based on the mass of dry ice and a mass-based
sublimation rate, the calculation takes into account the carbon dioxide
generated by the occupants in the passenger cabin. It also conservatively
assumes that all the carbon dioxide generated from the
sublimation of shipments of dry ice are distributed to the
passenger cabin.
Also, Boeing
presents other information in the form of graphs showing
the maximum suggested dry ice load for
various aircraft models and various assumed
sublimation rates in
percent of weight per hour. The service letter also suggests different
sublimation rates based on the type of packaging.
For example : Block of Dry Ice Wrapped in Paper
A 23-kg (50-lb)
block of dry ice wrapped in paper and exposed to an ambient temperature of
-18°C, a sublimation rate of 2% per hour is suggested; if the ambient
temperature condition is increased to 24°C, the recommended rate is
3% per hour.
As with Airbus, Boeing provides guidance but states that it is the responsibility of the operator[airline] to establish dry ice limits for their aircrafts.
Boeing dry ice limits
calculation is complicated!!
Maximum limitation for Dry Ice Per Cargo Compartment
This is a real example
to understand how airlines limits loading of dry ice on aircraft cargocompartments
Vietnam Airlines
Carbon dioxide solid
(Dry ice)
Loading of dry ice in
the same hold with live animals or hatching eggs must be limited. Dry
ice shall not be stowed above packages containing live animals and nearby of
live animals.
Maximum limitation for
Dry Ice per compartment of aircraft is as follows :
|
Aircraft type |
Compartment limit |
Aircraft limit |
Remarks |
|
A321
|
100
kg |
180
kg |
|
|
B777, B787/A330, A350
|
150
kg |
250
kg |
|
|
The maximum weight of Dry ice per aircraft is not allowed to be over Dry Ice for the two holds. For ATR72 aircrafts, Dry ice is not accepted except Dry ice used for refrigeration purposes, which total net quantities must not be exceeded 20 kg per flight. |
|||
The summary
FAA set the carbon
dioxide concentration limit for aircraft [CO2 ppm ] of 5,000 volume ppm. And
limited volume, % is 0.5. [ volume of equipped cabin or cargo compartment]
While
both Airbus and Boeing state that it is the
responsibility of the carrier to establish dry ice limits for
their airplanes. And of course, the carrier does their calculation and set the
limit and control the carriage of dry ice .
Safety
precautions must be taken when handling dry-ice because the
concentrated gas expels oxygen from the air in the confined spaces like
passenger's cabin / cargo compartments. Airlines
must give information to flight crews, other employees, handling
agents, information must include details of the location and
numbering system of cargo compartments together with
the maximum quantity of dry ice permitted in each compartment. Furthermore,
the airline must provide passengers with the dry-ice quantity
permitted and the method of packing which is accepted and any other
requirements.
If you wish to carry
frozen food with you while traveling by air , take a note that you must check
with your airline first and adhere to safety rules . Thank you for reading and
I will be happy to see your comments below.