Special Provisions (Section 4.4) & Mixture/Solution Rules

Special Provisions (Section 4.4) & Mixture/Solution Rules

While Section 4.2 provides standard classification and packaging entries for dangerous goods, many chemicals and manufactured articles possess unique physical, chemical, or operational characteristics that require tailored rules. DGR Section 4.4 (Special Provisions) provides specific instructions — all prefixed with the letter A — that override or supplement standard Section 4.2 requirements. Additionally, shippers frequently handle mixtures and solutions containing hazardous substances combined with non-hazardous solvents or secondary chemicals. Section 4.1 sets forth precise legal rules for naming and classifying these complex mixtures.

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1. Understanding Special Provisions (Section 4.4)

Column M of Section 4.2 — the Special Provisions column — contains alphanumeric codes starting with the letter 'A' (e.g., A1, A2, A67), listed vertically. Shippers must cross-reference these codes with Section 4.4 to verify whether special testing, packaging restrictions, State approvals, or full relief apply. A code shown in Column M applies to every packing group listed for that entry unless the wording of the provision says otherwise.

+-----------------------------------------------------------------------------------------+
|                                 Section 4.4 Special Provisions                          |
+-----------------------------------------------------------------------------------------+
                                             |
       +-------------------------------------+-------------------------------------+
       |                                                                           |
       v                                                                           v
+------------------------------------+                       +------------------------------------+
| Approval-Gated Provisions          |                       | Permissive / Exemptive Provisions  |
| (A1 = passenger aircraft route,    |                       | (e.g., A67 non-spillable batteries)|
| A2 = cargo aircraft only route)    |                       | Releases material from DGR rules   |
| Requires prior State approval      |                       | if specific conditions are met     |
+------------------------------------+                       +------------------------------------+

Mandatory vs. Permissive Special Provisions

1. Approval-Gated Special Provisions — these do not forbid; they open a door that is otherwise shut:

   • Special Provision A1: The entry shows Forbidden in the passenger aircraft columns (I and J). A1 permits carriage on a passenger aircraft with the prior approval of the appropriate authority of the State of Origin and the State of the Operator, under the written conditions those authorities set. The same entry may still be carried on a cargo aircraft under Columns K and L without invoking A1 at all.
   • Special Provision A2: The entry shows Forbidden in both the passenger and the cargo columns. A2 permits carriage on a cargo aircraft only with the prior approval of the State of Origin and the State of the Operator. Where other States have notified ICAO that they require it, approval must also be obtained from the States of transit, overflight and destination.
   • In both cases a copy of the document of approval, showing the quantity limitations and packing requirements, must accompany the consignment.

   Exam trap: A1 is the passenger aircraft route and A2 is the cargo aircraft only route. Candidates routinely reverse them.

2. Permissive / Exemptive Special Provisions:

   • Special Provision A67: Applies to non-spillable wet electric storage batteries. If the battery meets the vibration and pressure-differential criteria (no free-flowing electrolyte and no leakage of liquid), it is not subject to the DGR provided the terminals are protected against short circuits.
   • Certain special provisions must additionally be shown on the Shipper's Declaration whenever they apply. The DGR lists these explicitly: A1, A2, A4, A5, A51, A81, A88, A99, A130, A190, A191, A201, A202, A211, A212 and A331.

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2. Naming Single Dangerous Substance Mixtures & Solutions

When a dangerous good consists of a single predominant hazardous chemical dissolved in or mixed with non-hazardous substances (such as water or inert liquid), the DGR Section 4.1 mixture and solution rules govern Proper Shipping Name selection:

The Naming Rule

The mixture or solution must be identified by the Proper Shipping Name of the predominant dangerous substance, accompanied by the qualifying word "SOLUTION" or "MIXTURE" as appropriate, printed in bold uppercase.

• Example 1: Pure Acetone is declared as ACETONE (UN 1090). A mixture of 70% Acetone and 30% water is declared as ACETONE SOLUTION (UN 1090, Class 3, PG II).
• Example 2: Pure Nitromethane is declared as NITROMETHANE (UN 1261). A mixture of nitromethane with non-hazardous solvents is declared as NITROMETHANE MIXTURE.

Exceptions to the Naming Rule

The qualifying word "SOLUTION" or "MIXTURE" is NOT added if:

1. Section 4.2 specifically lists a separate PSN for the solution (e.g., ETHANOL SOLUTION is already explicitly listed under UN 1170).
2. The Section 4.2 entry for the pure substance expressly states that it applies only to the pure substance.
3. The addition of non-hazardous materials changes the hazard class, subsidiary risk, Packing Group, or physical state relative to the pure substance — in which case a different entry must be selected.
4. The hazard characteristics of the mixture call for different emergency response measures from those of the pure substance.

(Separately, if the dangerous constituent is so dilute that the mixture no longer meets the criteria of any hazard class, it is simply not a dangerous good and Section 4.2 does not apply at all.)

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3. Multi-Hazard Mixtures & Precedence of Hazards

When a mixture contains multiple hazardous constituents belonging to different hazard classes or divisions, determining the correct primary hazard class and Packing Group requires applying the Precedence of Hazards table (DGR Section 3.10).

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4. Packing Group Determination When Properties Differ

If physical testing of a chemical mixture reveals that its hazard characteristics (such as flash point, boiling point, or corrosive burn rate) differ significantly from the pure constituent listed in Section 4.2, the shipper must re-assign the Packing Group based on empirical test data:

• Flammable Liquids (Class 3): Packing Group I is triggered by the initial boiling point alone — any Class 3 liquid with an initial boiling point of 35°C or less is PG I whatever its flash point. PG II requires a flash point below 23°C and an initial boiling point above 35°C.
• Corrosives (Class 8): If a mixture causes full-thickness destruction of intact skin tissue after an exposure time of 3 minutes or less, observed within 60 minutes, it must be classified under PG I (Great Danger).

Shippers must never rely on theoretical assumptions when mixture properties alter the hazard severity level!