PED classification of substances as group 1 or group 2 using PED article 13 and Guideline B-41

Group 1 substances are defined as substances and mixtures that are classified as hazardous according to specific physical or health hazard classes, as outlined in PED Article 13, Classification of pressure equipment, in the CLP regulation No 1272/2008; or substances or mixtures with a maximum allowable temperature (TS) that exceeds the flash point of the fluid.

Group 2 substances are all other substances and mixtures not classified as group 1.

While group 1 is often simply referred to as "dangerous substances" and group 2 as "all others", the reality is more complex and not always as clear-cut as this categorization suggests.

It can sometimes be difficult to interpret PED article 13 to determine if a substance is group 1 or group 2, as just because a substance appears in the CLP regulation as hazardous, does not necessarily mean it is included in the specific hazard categories defined in article 13 that would make this group 1. Conversely, there are also examples where what is normally considered a non-hazardous substance may need to be categorized as group 1 due to the TS/flash point requirement of article 13.

This article will look at a few examples to show you how to classify substances using this.

Example 1: Ammonia (anhydrous), TS= 50°C (122°F)

Ammonia is listed in the CLP and has several hazard classes and category codes. It is common to use the hazard statement codes and cross reference these to guideline B-41. So, we have hazard statement codes H221, H331, H314 and H400. In Guideline B-41 it shows that hazard statement codes H221 and H331 meet the PED article 13 definition for classification as group 1, so ammonia would be classified as a group 1 substance on this basis. This is a classification of a substance that appears in the CLP regulation with hazard codes that are referenced by Guideline B-41.

Example 2: Propylene Glycol, TS= 150°C (302°F)

Propylene Glycol does not appear in the CLP regulation as it is considered non-hazardous. However, in article 13 there is another requirement to consider – that where the TS exceeds the flash point of the fluid. The flash point for Propylene Glycol is around 99°C (210°F) and our TS in this example is 150°C (302°F), so as TS is greater than the flash point, this would be classified as a group 1 substance on this basis. This is an example of where a non-hazardous substance that does not appear in the GLP regulation, and which would normally be seen as group 2, will need to be classified as group 1 based on its TS exceeding the flash point.

Example 3: Dimethyl formamide, TS= 50°C (122°F)

Dimethyl formamide is listed in the CLP and has several hazard classes and category codes: H360, H332, H312 and H319. Although these codes refer to specific hazards (e.g., H332 represents acute toxicity category 4, harmful if inhaled), none of these hazard codes are referred to by Guideline B-41 and so do not meet the PED article 13 definition for classification as group 1. The flash point of this substance is around 58°C (136°F), so the TS is also less than flash point. Based on this the substance is group 2. This is an example of a substance that appears in the CLP with several hazard codes (and so is considered a hazardous substance), but these hazards do not meet the criteria set in PED article 13 for them to be classified as a group 1 “dangerous substance” for PED. It is worth noting in this example that if the TS were to exceed the flash point, then this would change the classification from group 2 to group 1.

The examples show that when performing this classification, substances need checking to the CLP regulation and then cross referencing the hazard codes (or hazard statements) to those shown in PED guideline B-41 (or the statements in article 13). The CLP is periodically updated, so it is important to ensure this check is done to the latest version. In addition to this a check should always be made of the substances flash point against its TS value, as all substances with a TS above flash point are classified as group 1.