Committee of Experts on the Transport of Dangerous Goods and on the Globally Harmonized System of Classification and Labelling of Chemicals

Sub-Committee of Experts on the Transport of Dangerous Goods

Forty-first session

Geneva, 25 June – 4 July 2012
Item 3 (a) of the provisional agenda

Listing, classification and packing:
Proposals of amendments to the list of dangerous goods of Chapter 3.2

Proposal for classification criteria and packing requirements for gases adsorbed on solids

Transmitted by the Council on Safe Transportation of Hazardous Articles (COSTHA)

Introduction

1.The classification of gases adsorbed onto solid porous materials (adsorbents) was discussed at the fortieth session of the Sub-Committee (see informal document INF.42).  These materials are Class 2 gases adsorbed onto a non-hazardous solid porous material at less than 101.3 kPa at a temperature of 20 °C.

2. A summary of the comments resulting from the meeting discussions and background information of the packaging technology is included in the annex to this document.

I.  Explanation and justification of proposal

A. The Need for a new transport condition for gases adsorbed on a solid

3. A new transport condition for gases adsorbed onto a porous solid should be included in the regulations to accurately describe the physical state of a gas when in the adsorbed state. The physical properties of a gas in the adsorbed state differ significantly from when the gas is in the compressed or liquefied state due to the forces of attraction between the adsorbent and the adsorbed gas molecules.  These attractive forces result in a decrease in the energy normally possessed by gas molecules lessening the pressure of the gas compared to when it is the compressed or liquefied state. 

4. Several examples of how the adsorbed gas physical state differs from the state of the gas in other transport conditions are as follows:

(a) Methanegas can be transported as either a compressed gas or a refrigerated gas depending on how it is packaged and filled. The UN Model Regulations define a compressed gas as a substance which when packaged under pressure for transport is entirely gaseous at -50 °C; this category includes all gases with a critical temperature less than or equal to  -50 °C.  

In order to package methane as a compressed gas, mechanical energy via a compressor is applied to the gas in order to increase the number of gas molecules that can be contained in a pressure receptacle. To package methane in practical amounts, the gas must be at relatively high pressures, usually > 5000 kPa.When methane is adsorbed onto a carbon microporous material the gas does not require compression to fill appreciable amounts of gas into the container. For example, when 1.75 Kg of methane is compressed into a 50 liter cylinder, the resultant pressure is 5000 kPa whereas the same amount of methane adsorbed into a 50 liter container is < 101.3 kPa at 20 °C.

(b)Adsorbed gas packaging is generally more suited to liquefied gases as the properties of these gases favor more efficient adsorption than compressed gases.  Similar to the case of a compressed gas, energy must be provided for a gas to liquefy into a container.  For example, certain gases can be liquefied by either compressing or cooling the gas during the filling process.  Subsequent to liquefaction, the gas will remain liquefied by the force of its own vapor pressure inside the container.

An example of a gas that exhibits significant differences in the adsorbed state vs. the liquefied state is arsine.  Arsine is a highly toxic and flammable gas that is an important commodity used in the microelectronics industry to manufacture semiconductor devices.  Most consumer electronics, computers and automobiles incorporate electronic circuits that were fabricated using arsine in the manufacturing process.  Most of the arsine used in the microelectronic industry is provided using adsorbed gas packaging technology.

A typical liquefied gas package of arsine is a 2.2 liter cylinder containing 1200 grams of the gas under a pressure of 1400 kPa which is the vapor pressure of the liquid at 20 °C.  Since arsine has a critical temperature of 99.85 °C the state of the gas is considered to be a low pressure liquefied gas. 

When 1200 grams of arsine is packaged in a 2.2 liter cylinder containing a certain adsorbent, the pressure of the cylinder is < 101.3 kPa at 20 °C.   The dramatic reduction in pressure of the adsorbed gas package is a result of the interactive forces between the arsine gas and the adsorbent pores.   In this example, the arsine is not in a liquefied state, but is in an adsorbed state.  In addition to arsine, the following table shows the pressure comparison for several microelectronic gases in both the adsorbed state and liquefied gas state.  In each case the pressure in the adsorbed state is significantly less than the liquefied state.

B. New Entries to Dangerous Goods List

5. The proposal adds 6 new entries to the Dangerous Goods List to accommodate the different types of gases that can be adsorbed on porous solids.  The justification for these entries are as follows:

(a) Six new entries are necessary to assure that a UN number and a shipping name and description are available for each of the class 2 divisions as well as any subsidiary hazard combination associated with the primary hazard. 

(b) Generic descriptions were chosen to limit the number of UN numbers needed as there are many gases that can be adsorbed on solids.

(c) The new generic entries will require a technical name in brackets immediately following the new shipping name and description as indicated by special provision 274 in column 6 for the new dangerous good list entries.

(d) Generic entries would appear more plausible than specific entries for each gas as there are > 10 gases routinely packaged in the adsorbed gas package.   We anticipate further proliferation of the technology to other gases over time which would result in additional modifications to the regulations each time a new gas is introduced in the adsorbed gas packaging format.  A current list of the commercially important gases shipped in the adsorbed gas state include:

6.  A new special provision “XYZ” is needed to set forth proper controls to assure the safe packaging and transportation of adsorbed gas packages.

(a) The purpose of the first statement in the new special provision “XYZ” is to provide controls that limit the pressure of the adsorbed gas package.  The control specifies that under the conditions of normal temperature and pressure (NTP), the packaging when completely filled and closed will not exceed an absolute internal pressure of 101.3 kPa at 20 °C.  The term “thermally equilibrated” assures the entire contents (gas and adsorbent) of the package are at a uniform temperature of 20 °C.  Additionally, when the packaging is completely filled and closed, the pressure cannot exceed 300 kPa at 50 °C; and at any time during the normal condition of transport, the internal pressure of the pressure receptacle cannot exceed the working pressure; and at any time, the pressure of the receptacle cannot exceed the test pressure at 65 °C.

(b) The second and third statement of special provision “XYZ” provide controls to make sure the adsorbent is compatible with the gas and cylinder and that the combined adsorbent-gas system is also compatible with the cylinder. 

(c) The fourth statement is necessary to specify the unique leak testing required for an adsorbent gas package containing a Class 2 gas which is described in ISO 11513:2011.

(d) The fifth statement specifies the requirements for filling as specified in ISO 11513:2011

(e) The sixth statement specifies the requirements for periodic inspection and test as specified in ISO 11513:2011. 

D. New Packing Instruction “P2YY”

7. The new packing instruction “P2YY” is needed to provide packing instructions unique to gas adsorbed on a microporous solid.

(a) The first instruction specifies which cylinders and pressure receptacles are authorized for packaging adsorbed gases.   Competent authority approved cylinders are included in a similar fashion to packing instruction P201.  Cylinders meeting the requirements of ISO 11513:2011 are included as this design standard enables the use of monolithic adsorbents that require a welded cylinder design.  Cylinders meeting the requirements of ISO 9809-1:1999 are included as these are commonly used for adsorbed gas packages employing granular adsorbents that can be filled into standard cylinder openings.

(b) The packing instruction limits the fill pressure of an adsorbed gas package to < 101.3 kPa at 20°C which is an important control to assure that packages are pressureless.

(c) A minimum test pressure of 21.7 bar has been specified which is seven times greater than the internal pressure the cylinder is allowed to develop at 50°C.(d) A minimum burst pressure of 94.5 bar is equal to that specified in ISO 11513:2011.

(e) For Division 2.3 gases with a LC50 < 200 mg/m³ (ppm), the requirements specified in special packaging provision “k” in P200 apply to the new packing instruction.

(f)  Gas tight plugs or caps are required for pyrophoric gases adsorbed on a porous solid, which is a prudent practice.

(g) Since the current proposal includes gases where the special provisions a-d of P200 would be applied for compressed gases, it is sensible to apply the same provisions when these gases are adsorbed on a solid to assure the ladings are compatible with the container.

(h) A 10 year periodic inspection interval is suggested as the adsorbed gas packages are pressureless and not prone to failure caused by the combination of pressure and mechanical defects in the cylinder.

8.  As a result of the previous justifications and comments made at the fortieth session of the Sub-Committee, COSTHA proposes the following amendments to the Model Regulations.

II.  Proposals

9. Amend 2.2.1.2 to include a new transport condition of a gas as follows:

“ (e) Gas adsorbed onto a porous solid—a gas which when packaged for transport is adsorbed onto a solid porous material resulting in an internal receptacle pressure of < 101.3  kPa at 20 °C and less than 300 kPa at 50 °C.”

10.  Create six new entries (UN 3XXX, UN 3YYY, UN 3AAA, UN 3BBB, UN 3CCC and 3DDD) in Class 2.

(a) Add six new entries to the Dangerous Goods List, as follows:

(b) Add the six new N.O.S. entries to Appendix A

11. Add a new special provision XYZ in Chapter 3.3

XYZ: This entry applies to gases of Class 2 adsorbed onto a solid porous material inside a pressure receptacle with a closure.  

The pressure receptacle containing the adsorbed gas shall be at a pressure less than 101.3 kPa at the time the filled pressure receptacle is closed and thermally equilibrated to 20 °C.   The internal pressure of the filled pressure receptacle shall not exceed 300 kPa at 50 °C.  At any time during the normal condition of transport, the internal pressure of the pressure receptacle cannot exceed the working pressure of the cylinder. In no case shall the internal pressure at 65 °C exceed the test pressure of the pressure receptacle.

The adsorbent material shall be compatible with the pressure receptacle and does not form harmful or dangerous compounds with the gas to be adsorbed. 

The gas in combination with the adsorbent material shall not affect or weaken the pressure receptacle or cause a dangerous effect (e.g. catalyzing a reaction).

The adsorbent material shall not meet the definition of any of the hazard classes in these Regulations.

Each cylinder shall be leak tested using a helium leak test as specified in ISO 11513:2011.

The filling procedure shall be in accordance with Annex A of ISO 11513:2011.

Periodic inspection and test shall be in accordance with Annex B of ISO 11513:2011.

12. Add a new packing instruction P2YY as follows:

13. Amend 6.2.1.1.5 as follows:

The test pressure of cylinders, tubes, pressure drums and bundles of cylinders shall be in accordance with packing instructions P 200, or, for a chemical under pressure, with packing instruction P206.  The test pressure of a closed cryogenic receptacle shall be in accordance with packing instruction P203.  The test pressure of a metal hydride storage system shall be in accordance with packing instruction P205.  The test pressure of the cylinder for a gas adsorbed on a solid shall be in accordance with P2YY.

14.  Add ISO 11513:2011 to the table listing UN cylinders in 6.2.2.1.1

Annex

Discussions Held in Previous UN Meeting and General Product Information

In December 2011, COSTHA presented an informal paper (40/INF.42) to the UN/SCETDG on adsorbed toxic gases. Those commenting on INF 42/COSTHA agreed that adsorbed gases were not adequately addressed in the Model Regulations but preferred  retaining a classification calling these materials gases rather than [toxic] solids. A formal summary of comments from the meeting was published and is cited below:

Comments from UN/SCETDG COSHTA Informal Paper

ADSORBED TOXIC GASES

(UN/SCETDG/40/INF.42 – COSTHA) – In this information paper COSTHA questioned whether adsorbed gas technology was adequately addressed in the Model Regulations through this INF paper.  Specifically, COSTHA requested comments from the Sub-Committee as to whether adsorbed gases should be considered gases or whether they more resemble solids.  While time was short, Canadaand Austriaprovided specific comments that adsorbed gases are not adequately addressed, and individual entries for such gases may be necessary to adequately address.  However both Canadaand Austriawere adamant that the material was in fact a gas and should, at least at this stage, remain classified as a toxic gas.  These comments were in alignment with comments received earlier in the week from CGA and EIGA.  The Chairman noted additional comments would be welcome in the margins of the meeting or following the session via email.

Information on the products being considered

Traditionally, gases are compressed or liquefied under high pressure and contained within a pressure rated cylinder.  Gas under pressure is extremely hazardous as the contents can escape if the cylinder or the valve is damaged during transport, resulting in a release of highly toxic, flammable and/or corrosive gas to the environment.  Due to this inherent hazard, the packaging and transportation of hazardous gases is tightly regulated to protect life, property and the environment. 

Technology advances in the area of gas stabilization have resulted in packaging systems where internal cylinder pressures are at or below atmospheric conditions.  The practice of [reversibly] adsorbing the gas onto a porous solid [adsorbent] has grown as a means to transport hazardous gases in a safer condition, relative to traditional compressed gas or liquefied gas cylinders.  In practice, end-users apply a vacuum to the cylinder to provide the motive force to reverse the gas/solid complex and to pull the vapor out. The packaging consists of a metal cylinder shell filled with an adsorbent material, an end cap welded to the cylinder shell and a cylinder valve.  Figure 1 is an example of an adsorbed gas packaging system.

When gases are adsorbed onto a porous solid, the following changes in gas properties and conditions take place.

1. Relative to conventional high pressure gases, when adsorbed on a porous solid, gases exist in a more stable condition within the matrix. Energy is released during the adsorption process. Pressure is dramatically reduced as the gas "complexes" with the solid [typically a highly activated pure carbon].  As a result, the stabilized gas exhibits a reduced chemical reactivity with respect to oxidation and/or deflagration. For example, when germane (UN 2192) is adsorbed on a solid, experiments have shown a deflagration reaction cannot be initiated by an electrical arc. When this same experiment is carried out with pressurized germane, all of the germane decomposes to elemental hydrogen and germanium metal.

2. Maximum pressures expected during transport [50 °C] are low and shown in Figure 2 for a sample of Class 2.3 gases commonly being transported in the adsorbed state.  As temperature is increased, the added thermal energy causes some of the adsorbed gas to be desorbed and results in a modest "gas under pressure" condition.  Typically this occurs at or above 26 °C. Cooling the cylinder back below this crossover temperature restores the cylinder to a sub-atmospheric pressure state.  The maximum pressure reached at 50 °C is ~ 240 kPa (35 psia) for each of the gases

As the main purpose is to store and transport highly toxic materials, the threat of inhalation and poisoning is present with adsorbed gas packages at temperatures above 26 °C.   For that reason, a Class 2 classification is maintained.

3. Another characteristic of adsorbed gases is that only a fraction of the total stored gas inventory would be lost during a release incident.  A compressed gas package has the potential to rapidly lose 100% the stored inventory from failed or compromised packaging.   In contrast, the adsorbed gas packaging’s porous solid exerts attractive forces on the gas and therefore losses to the environment are less.   Because the pressure driver is much lower with an adsorbed gas, release rates are also proportionately lower. 

4. Adsorbed gas cylinders are less likely to fail in a fire situation because the porous solid acts as both a thermal insulator and a heat sink.  In simulated fire testing, cylinders containing gas adsorbed onto a porous solid survived three times longer than comparable high pressure cylinders over a broad range of test temperatures.   Figure 3 shows the results of fire testing for standard pressurized liquefied cylinders of phosphine and phosphine adsorbed on a porous solid.  The cylinders used in the tests contained equal amounts of phosphine (500 grams) in 2 liter cylinders. 

5. The porous solid is typically a high surface area activated carbon.  Purity must be high as to not contribute to decomposition of the stored gas.  The porous solid can be of many shapes and sizes from granular to shaped monoliths.  When shaped sorbents are used, a welded steel cylinder like that specified in ISO 11513:2011 is used for containment.  Tests should be run to show the porous solid is stable with any gas to be adsorbed under the conditions of normal transport and use.  Figure 4 shows the various adsorbent form factors used in adsorbed gas packagings. The picture shows examples of monolithic, bead, pellet and tablet carbon adsorbents.

联合国危险货物运输专家和全球化学品统一分类和标签制度专家委员会

危险货物运输专家分委员会

第四十一次会议

日内瓦, 2012年6月25日-7月4日
议程第3 (a)项

列表、分类和包装：

对3.2章危险货物列表的修订提案

关于吸附在固体上的气体的分类标准和包装要求的提案

由危险物品安全运输委员会（COSTHA）提交

              介绍

              1.  吸附在固体多孔物质（吸附剂）上的气体的分类在分委员会第四十次会议上已进行过讨论（见非正式文件INF.42）。这些物质是指在小于101.3kPa，20℃时，吸附在无危险性的固体多孔物质上的第2类气体。

        2.  本文件的附件中包含了上次会议讨论得出的意见总结和包装技术的背景信息。

              I .  提案的说明与论证

             A. 吸附在固体上的气体需要采用新的运输条件

3 . 规章范本中应当包括针对吸附在多孔固体上的气体的新的运输条件，以便精确描述在吸附状态下气体的物理状态。在吸附状态下，气体的物理性质与其在压缩或液化状态下相比有着很大区别，这是由吸附剂与其吸附的气体分子之间的吸引力所造成的。与通常压缩或液化状态时相比，这种吸引力使得气体分子较通常情况下所具有的能量降低，气体压力减小。

4.  下述例子阐释了吸附气体的物理状态与其他运输条件下气体状态的不同。

               (a) 甲烷气体根据其包装与装载方式既可作为压缩气体也可作为冷冻气体进行运输。联合国规章范本定义压缩气体为在-50℃下加压包装进行运输的，完全处于气态的气体；这一类别包括临界温度小于或等于-50℃的所有气体。

为了将甲烷作为压缩气体包装，会利用压缩装置的机械能以使压力贮器中可以装载的气体分子数增加。为了能够包装具有实用数量的甲烷，气体必须处于相对较高的压力下，通常压力要> 5000 kPa。

当甲烷吸附在碳多微孔材料上时，不需要经过压缩以将可观的数量气体装载入容器中。例如，在20 °C 时，当1.75kg甲烷被压缩到一个50升气瓶中时，产生的压力为5000kPa，而吸附在50升容器中的相同数量的甲烷所产生的压力在20℃时小于 101.3 kPa。

              (b) 吸附气体包装通常情况下更适合液化气体，因为液化气体的性质与压缩气体相比有利于更加有效的吸附。与压缩气体的情况类似，必须提供能量使气体液化并装入容器。例如，特定气体的液化可以通过压缩或在装载过程中的气体冷却来实现。液化之后，气体将由于容器中其自身的蒸气压而保持液化状态。

一些气体在吸附状态下和在液化状态下呈现出显著的不同，胂便是一个例子。胂是一种高毒、可燃性气体，是一种在微电子工业中用于制造半导体器件的重要商品。大多数消费类电子产品、计算机和汽车，在制造过程中均采用胂制备的电子电路。大部分在微电子工业中使用的胂是利用吸附气体包装技术提供的。

胂的一个典型液化气体包装为2.2升的气瓶，包含1200克气体，压力1400kPa，这也是20°C时液体的蒸气压。由于胂的临界温度为99.85°C，气体状态被认为是低压液化气体。

当1200克胂装载入一个2.2升装有特定吸附剂的气瓶中时，20 °C时气瓶中压力< 101.3 kPa。之所以相比而言，吸附气体包装内的压力有如此显著的下降，是因为气体与吸附气孔间具有的相互作用力。在此例中，胂并不处于液化状态，而是处于吸附状态。除了胂，下列表格显示了几种微电子气体在吸附状态与液化状态下的压力比较。每一例中，吸附状态的压力都要显著地小于液化状态。

B．危险货物列表中新增条目

5.   提议在危险货物列表中新增6个条目以适应不同种类的可吸附于多孔固体上的气体。关于新增条目的论证如下所示：

 (a)  六个新的条目对于确保每一个第2类以及任何与主危险性组合关联的副危险性都有对应的UN编号、名称与说明是必要的。

 (b)  选择通用名称以限制所需UN编号的数目，因为可吸附于固体的气体种类很多。

 (c) 对于危险货物列表中新增的条目，在第6栏中有特殊规定274，新增的一般名称将需要在新的运输名称和说明之后紧接着在括号中列明技术名称。

 (d)   通用条目较对于每一种气体而言的特定条目更具可行性，因为有> 10种气体可常规地使用吸附气体包装。我们预见到该技术随着时间将会得到进一步的拓展，因此，将来每一次一种新的气体引入吸附气体的包装模式时，法规都需进行附加修订。目前，商业上较为重要的在吸附气体状态下运输的气体名录包括：

       C. 新的特殊规定 “XYZ”

                   6.   需要制定一条新的特殊规定 “XYZ”详细说明适当的控制以确保吸附气体包装的安全包装和运输。

(a) 新的特殊规定“XYZ”中的第一个语句的目的是提供控制信息以限制吸附气体包装的压力。控制信息详细说明了在常温常压下（NTP），完全充满并密封的包装的绝对内压在20 °C时不能超过101.3 kPa。术语“热平衡”保证了包装中所有内容物（气体和吸附剂）都处于一致的温度下，即20 °C。此外，当包装完全充满并密闭时，在50 °C时的压力不能超过300 kPa；并且在正常运输条件下，任何时候压力贮器的内压均不能超过工作压力；并且在任何时候，贮器的压力都不能超过65 °C时的试验压力。

(b) 特殊规定“XYZ”中的第二和第三条语句提供控制信息以确保吸附剂与气体和气瓶相适应并且吸附剂-气体组合系统也与气瓶相适应。

(c) 第四条语句是必要的，它详述了装有第2类气体的吸附气体包装的特定泄漏试验，该试验在ISO 11513:2011中有描述。

(d) 第五条语句说明了装载要求，该要求在ISO 11513:2011中有规定。

(e) 第六条语句说明了定期检查和试验的要求，该要求在ISO 11513:2011中有规定。

                    D.   新包装说明“P2YY”

  7.   需要采用新包装说明“P2YY”提供适用于吸附在多微孔固体上的气体的特定包装说明。

(a)  第一条说明规定了何种气瓶和压力贮器可被批准装载吸附气体。主管当局认可的气瓶被收录其中，收录形式与包装说明P201相似。符合ISO 11513:2011要求的气瓶包含其中，因为这种设计标准允许使用块体吸附剂，而这种吸附剂需要一种焊接气瓶设计。符合ISO 9809-1:1999要求的气瓶被收录其中，因为这些气瓶通常用于使用颗粒状吸附剂的吸附气体包装，其中颗粒状吸附剂可从标准气瓶开口中装入。

(b)  包装说明限制了吸附气体包件的填充压力在20°C时< 101.3 kPa，此规定对于确保包件无压力具有重要的控制作用。

(c)  规定了最小试验压力为21.7 bar，这一数值比50°C时所允许的气瓶内压高7倍。

(d)   最小破裂压力94.5 bar与ISO 11513:2011的规定一致。

(e)   对于项别2.3的气体（LC₅₀ < 200 mg/m³ (ppm)），P200中的特殊包装规定“k”的要求适用于新包装说明。

(f)     吸附在多孔固体上的发火气体需要气密塞或盖，此操作需谨慎。

 (g)   由于当前的提议中认为P200的a-d特殊条款应该适用于压缩气体，所以这些气体在吸附于固体上的情况下，为保证装载与容器匹配，同样的规定也应适用。

(h)  建议定期检查的间隔为10年，因为吸附气体的包件无压力且不易出现由压力和机械缺陷共同造成的损坏。

  8.     基于第四十次分委员会的论证和意见，危险物品安全运输委员会（COSTHA）提出了以下规章范本的修订意见。

                   Ⅱ．提议

　　　         9.   修订2.2.1.2，新增气体运输条件如下：

“(e)  吸附于多孔固体上的气体—— 吸附于多孔固体物质的气体包装运输时，使得温度20 ℃时，贮器内压<101.3kPa且在 50 ℃时，低于200kPa.”

                    10.  第2类新设六个条目(UN 3XXX, UN 3YYY, UN 3AAA, UN 3BBB, UN 3CCC and 3DDD)。

                  （a）危险货物列表新增如下六个条目：

                    (b) 附录A新增六个新的未另列明的(N.O.S.)条目

                     11.3.3章新增特殊规定XYZ

                     XYZ：此条目适用于封闭在压力贮器中，吸附在多孔固体上的第2类气体。

                    含有吸附气体的压力贮器在装填压力贮器密闭并达到20 °C的热力学平衡时，其压力应小于101.3 kPa。装填压力贮器的内压在50 °C时不应超过300 kPa。在正常运输条件下，无论何时，装填压力贮器的内压都不能超过气瓶的工作压力。任何情况下65 °C时的内压都不应超过压力贮器的试验压力。

                    吸附材料应适合于压力贮器并且不与被吸附气体生成有害或危险性化合物。

                    与吸附材料结合的气体不应影响或削弱压力贮器或导致危险效应（比如催化某种反应）。

                    吸附物质不应符合这些规章中任何一类危险品的定义。

                    每个气瓶都应按照ISO 11513:2011的规定进行氦泄漏试验。

                    装载过程应与ISO 11513:2011附件A的规定相一致。

                    定期检查和试验应与ISO 11513:2011附件B的规定相一致。

                    12. 新增包装说明P2YY如下：

                     13. 6.2.1.1.5修订如下：

气瓶、气筒、压力桶和气瓶捆包的试验压力必须符合包装说明P200 的规定，而对于压力下的化学品，则遵循P206的包装说明。封闭式低温贮器的试验压力应与P203的包装说明一致。封闭低温贮器的试验压力，必须符合包装说明P203 的规定。金属氢贮存系统的试验压力，必须符合包装说明P205 的规定。吸附在固体上的气体，其气瓶试验压力必须符合包装说明P2YY规定。

                     14. 在6.2.2.1.1的UN气瓶列表部分添加ISO 11513:2011。

附件

往届联合国会议讨论和一般产品信息

2011年12月，危险物品安全运输委员会（COSTHA）向UN/SCETDG呈递了关于有毒吸附气体的非正式文件(40/INF.42)。非正式文件(40/INF.42)的评论认为吸附气体在规章范本中并没有明确说明，但是仍应保留其气体而非（有毒）固体的分类形式。以下引自正式会议意见概要：

关于UN/SCETDG COSHTA非正式文件的评论

有毒吸附气体

(UN/SCETDG/40/INF.42 – COSTHA)——通过这个非正式文件，危险物品安全运输委员会（COSTHA）质疑吸附气体技术是否已在规章范本中明确说明。危险物品安全运输委员会（COSTHA）还特别要求分委员会给出意见，判定该吸附气体到底应该被视为气体还是固体。虽然时间较短，加拿大和澳大利亚还是提供了具体的意见：吸附气体并没有在规章范本中得以明确说明，在规章范本中针对于这些气体给予单个条目可能是有必要的。但是加拿大和澳大利亚都坚持该物质事实上是气体，至少在该阶段应仍然被划分到有毒气体类别中。这些与一周前从压缩气体协会（CGA）和 欧洲工业气体协会(EIGA)得到的意见达成一致。 委员会主席指出，在会议间歇或会后，委员会仍然欢迎各方通过邮件发表更多意见。

纳入考虑的产品信息

通常，气体被压缩或高压液化后， 装入额定压力的气瓶中。高压气体极度危险，一旦气瓶或阀门在运输途中损坏，将释放剧毒性、易燃和（或）腐蚀性气体。由于这一固有风险，危险气体的包装和运输要严格控制，以保护生命、财产和环境安全。

气体稳定性方面的技术进步使包装系统的气罐内压得以等于或低于大气压力。与传统的压缩气罐或液化气罐相比，（可逆地）将气体吸附在多孔固体（吸附剂）的做法已经成为运输危险气体的一种更安全的方式。在实践中，终端用户运用气罐抽真空为气体/固体络合物的转换提供原动力，并把蒸气抽出。包装由装载吸附物质的金属气瓶壳，一个焊接在罐壳上的端盖和一个气罐阀门组成。图1为吸附气体包装系统的一个示例。

当气体被吸附于多孔固体上，气体特性和状态将发生以下改变。

1.  与传统的高压气体相比，当吸附于多孔固体上时，气体将处于更为稳定的状态。能量在吸附过程中被释放。由于气体与固体（典型的固体如高活性碳）成为复合体，压力急剧降低。因此，气体氧化或爆燃的化学反应性降低。比如，实验显示，当锗烷(UN 2192)被吸附于固体上，电弧无法引发爆燃反应。如果用受压的锗烷做同样的实验，所有锗烷都将分解成氢元素和锗金属。

2.  运输过程中（50 °C）的最大压力很低，图2中是通常以吸附状态运输的2.3类气体样本。随着温度升高，增加的热能将导致部分吸附气体解吸，转变为“受压气体”状态。通常这种情况会发生在温度大于等于26 °C时。将气瓶冷却至26 °C这一临界温度以下将使其恢复负压状态。温度50 °C时，每种气体的最大压力为240 kPa (35 psia)。

由于吸附气体包装主要目的是储存和运输高毒物质，当气体吸附包件温度高于26 °C时，会存在吸入和中毒风险。因此，保持第2类的分类。

3. 吸附气体的另一个特性是，如不慎泄漏，储存气体只会流失一小部分。压缩气体包装如果损坏，则可能会迅速流失相当于储存量100%的气体。相反的，吸附气体包装的多孔固体对气体施以引力，流失至环境中的气体会减少。因为吸附气体的压差较低，释放比例相应也更低。

4．吸附气体气瓶遇火灾也不易出现问题，因为多孔固体可以充当热绝缘体和散热器。在模拟火灾试验中，装有吸附在多孔固体上气体的气瓶在较宽的温度范围内比同类高压气瓶承受的时间要长三倍。图3显示标准的受压液化膦气瓶和吸附于多孔固体上的膦在火灾试验中的结果。测试中的2升气瓶中装有同样数量的磷化氢（500克）。

5.  典型的多孔固体是高比表面积活性碳。其纯度必须很高以避免因纯度因素造成储存气体的分解。多孔固体有多种形状和大小，可以是颗粒状的，也可以是块状材料。运用成形的吸附剂时，使用ISO 11513:2011指定的焊接钢制气瓶用于储存。试验应显示出正常运输和使用中，任何气体吸附其上，吸附有气体的多孔固体都是稳定的。图4为多种形状因数的用于吸附气体包装的吸附剂。图中给出了块状、珠状、小球状和片状的碳吸附剂。