Why the ‘Y’ in the Air Limited Quantity Mark

As a dangerous goods (DG) instructor for over ten years, I often wondered: “Why the ‘Y’ in the air limited quantity mark?”  In other words, why not an “L” for limited quantity; or perhaps an “A” for air acceptable?  I pondered this question through many a class without an answer.  Interestingly, in all those years, not a single student ever asked me about this question.  Did anyone but me even care?   Of course, the fact that the IATA limited quantity packing instructions (PI) also use the “Y” as a prefix, such as PI “Y341” (for limited quantities of flammable liquids), might be a clue.

Finally, I couldn’t take not knowing any longer!  So my research began with a call to Katherine at the US DOT Hazmat Hotline, who could only tell me that they “were not sure.”  Next, I scoured the domestic and international DG regulations with no luck.  Finally, out of the blue, while attending a recent European Highway Regulations (ADR) seminar, the instructor made mention of the age-old question regarding the “Y” in the limited quantity mark.  He said that it was related to the 1.2 meter drop test required for limited quantity packages shipped by air.  This made sense, as the drop test requirements for UN specification packagings require an “X” for packing group I; a “Y” for packing group II; and a “Z” for packing group III.  The corresponding drop heights for these are expressed in meters as follows: 1.8 m, PG I; 1.2 m, PG II; and .8 m, PG III.

On a final note, it is interesting to point out that DOT Chart 16, a compendium to 49 CFR which shows the actual colors and details of required markings, labels and placards, incorrectly states that the limited quantity mark with the “Y” included is for “Air Only,” but in actuality, it should say for “All Modes” – including air.  The mark absent the “Y” states, “All other Modes,” referring to ocean, highway and rail (as noted in 49 CFR 172.315, Limited Quantities, “Modes other than air transport”).  Perhaps they will correct this when DOT Chart 17 is released.