Dry Ice | Why Loading of Dry Ice Is Limited On Aircraft

 

Dry-ice is solid carbon dioxide [ Hazmat class 9, UN 1845], It is carried by air passengers in hand carried bags or in checked baggage with approval of the airline. Dry ice is shipped as cargo and used primarily as a cooling agent. Its advantages include lower temperatures than that of water ice and not leaving any residue. Dry Ice sublimes [passes directly into the vapour without melting] at −78.5 °C .

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:

§Tiredness

§  Fatigue.

 

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.