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1.0 Who is this guidance for?
This guidance is for a person conducting a business or undertaking (PCBU). It is for PCBUs that want to work out, based on the hazardous substances they use, make or hold:
- whether their workplace requires a ‘hazardous substance location’ (HSL)
- whether they will need a location compliance certificate (LCC).
2.0 What does this guidance cover?
This guidance shows how to use a formula that calculates the sum of ratios (called the quantity-ratio sum – QRS).
This ratio determines whether your workplace requires an HSL or needs an LCC. This is provided for in regulation 10 of the Health and Safety at Work (Hazardous Substances) Regulations 2017 (the Hazardous Substances Regulations).
This guidance:
- explains what you need to know to calculate the QRS
- explains how to calculate the QRS
- provides worked examples.
3.0 When does this guidance not apply?
This guidance does not cover class 1 explosives. Regulation 10(6)(external link) describes the QRS requirements for explosives.
Where compliance certification is required at any amount of a substance or based on the capacity of the container (for example, certification of tank wagons or stationary containers systems), the QRS will not need to be applied. An example of this is class 6.1A substances, where any amount of a 6.1A substance is required to be under the control of a certified handler.
The guidance only applies to location compliance certification. It does not apply to certification of:
- tank wagons
- stationary container systems
- certified handlers.
The QRS is also not used in determining requirements for thresholds that do not require certification (for example, for signage). Regulation 10(1) refers to the QRS being used to determine whether the requirement for an HSL or an LCC is activated.
4.0 What are location compliance certificates (LCCs)?
Compliance certifiers are authorised by WorkSafe New Zealand to issue compliance certificates required by the Hazardous Substances Regulations for matters that are within the scope of their authorisation. Compliance certificates may be required for people, locations, plant, buildings or equipment.
You can find a list of compliance certifiers at Register of compliance certifiers(external link) You can filter this list to find a certifier that fits your situation.
Compliance certifiers charge for their work. The cost of issuing compliance certificates varies between compliance certifiers. You should contact several certifiers to discuss the services they offer and their fees.
When may you need an LCC?
You may require an LCC if you have explosive, flammable, oxidising, toxic or corrosive substances, and the quantity exceeds the thresholds specified in the Hazardous Substances Regulations.
An LCC certifies that the HSL where the substances are used and stored is managed according to the rules.
Further details on LCC can be found at Location compliance certificates
5.0 What do you need to calculate the QRS?
You need to find out what hazardous substances you have, their hazard classifications, and quantity held.
You can find the classifications from the substances’ SDSs (safety data sheets). Depending on how old the SDS is, the classification listed may either be the pre-30 April 2021 HSNO classification or the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).
For the QRS calculation, you will need the pre-30 April 2021 HSNO classification as these are the classifications used in the Hazardous Substances Regulations.
About pre-30 April HSNO classification and GHS classification, and converting between the classifications
For the pre-30 April 2021 HSNO classification, substances were assigned:
- Numbered Classes: These classes (for example, class 3, class 6) indicate the inherent hazardous properties of a substance.
- Numbered Subclasses: These subclasses (for example, subclass 3.1, subclass 6.1) specify the type of hazard posed by a substance.
- Lettered Categories: These categories (for example, category A) indicate the severity of the hazard posed by a substance.
For the GHS classification, the substances (except for class 1 explosives) are assigned hazard descriptors and categories or types.
To convert a GHS classification to the pre-30 April 2021 HSNO classification, use this table HSNO-GHS 7 Correlation Tables(external link)
For example:
- GHS flammable gas Category 1 = pre-30 April 2021 HSNO class 2.1.1A
- GHS skin corrosion Category 1B = pre-30 April 2021 HSNO class 8.2B.
See Appendix 1 for more information about pre-30 April 2021 HSNO classifications.
6.0 How can you calculate the QRS?
What is the QRS formula?
The QRS is calculated using the following formula:
QRS = Σ [qpi/qai]
= (quantity held of classification A/threshold for classification A) + (quantity held for classification B/threshold for classification B)+…
This involves working out the ratio of the amounts of hazardous substances for each hazard classification you have, divided by their threshold value (from the Hazardous Substances Regulations), and then adding it to other relevant ratios (see below).
- If the QRS is >1, the threshold has been exceeded – the site has triggered the requirement for an HSL and/or an LCC.
- If the QRS is 1 or less than 1, the threshold has not been exceeded – the site has not triggered the requirement for an HSL and/or an LCC.
Which ratios should be added together in the QRS?
Generally, you should add together the amounts of substances you have for each classification. Then use this amount to calculate the ratio for each classification. The ratios from substances of the same subclass are then added together to calculate the final QRS of each subclass. However, there are exceptions:
- Not all hazard classifications within a subclass should be added together or included in the QRS calculation. Table 1 shows which hazard classifications for each subclass can be added together in the QRS calculation.
- For some classifications, the thresholds are dependent on container size or whether the container is open or closed. When there is a different threshold for substances of the same subclass, calculate the ratios separately for these.
- If substances would need to be stored in different HSLs (for example, class 5.1.1 substances ‘manufactured or used’ and substances ‘in packages that are closed at all times’), the QRS values must be calculated separately and not added together. This also applies to class 5.1.2 and 5.2 substances.
- Class 6 and 8 substances are added together unless the substances are incompatible. When class 6 and 8 substances are incompatible, they must be segregated and stored at separate HSLs. This means they are not added together when calculating the QRS (see regulation 13.29 and Schedule 15 Incompatible substances(external link) for details, as well as the SDS for incompatibilities).
Section 7 provides worked examples.
Table 1: Hazard classifications that can be added together in the QRS calculation
7.0 Where can you find examples showing how to calculate QRS values for different classes of substances?
The following examples show how to calculate QRS values of class 3, 5, 6 and 8 substances.
Examples of the QRS calculations with only class 3 substances
Example: Class 3.1A substance and class 3.1B substance in closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 1 x 10 L container of acetaldehyde (a 3.1A substance) in a closed container
- 4 x 20 L containers of isopropanol (a 3.1B substance) in closed containers.
Regulation 10.26 sets out a PCBU’s duty to establish an HSL for class 3 substances(external link)
- The threshold quantity for a 3.1A substance that is not petrol, aviation gasoline, or racing gasoline = 20 L; for a 3.1B substance in closed containers more than 5 L is 100 L (From Table 4 Schedule 9: Quantities of classes 2–4 substances that activate HSL requirements(external link)).
| Substance | Classification | Amount held | Threshold (for an HSL) | Ratio |
| Acetaldehyde | 3.1A | 10 L (1 x 10 L) | 20 L (in open or closed containers) | 0.5 (10 L/20 L) |
| Isopropanol | 3.1B | 80 L (4 x 20 L) | 100 L (in closed containers more than 5 L) | 0.8 (80 L/100 L) |
| QRS | 1.3 (0.5 + 0.8) |
For classes 1–5, substances of the same subclass are added together. After adding the ratios together, the QRS is 1.3. This means that the HSL threshold has been exceeded and the workplace requires an HSL. An LCC is also required.
Note there are class 3.1 threshold variations for fuel and pesticides on a farm.
Example: Multiple class 3.1B and 3.1C substances in closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 1 x 20 L of Substance A (class 3.1B) in a closed container
- 2 x 10 L of Substance B (class 3.1B) in closed containers
- 5 x 10 L of Substance C (class 3.1B) in closed containers
- 5 x 20 L of Substance D (class 3.1C) in closed container
- 2 x 100 L of Substance E (class 3.1C) in closed containers.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
| Classification | Total amount held | Threshold for an HSL* | Ratio |
| 3.1B | 90 L (1 x 20 L + 2 x 10 L + 5 x 10 L) | 100 L (in closed containers more than 5 L) | 0.9 (90/100) |
| 3.1C | 300 L (5 x 20 L + 2 x 100 L) | 500 L (in closed containers more than 5 L) | 0.6 (300/500) |
| QRS | 1.5 |
For classes 1–5, substances of the same subclass are added together. As the QRS is greater than 1 (1.5), the HSL threshold has been exceeded and the site requires an HSL. An LCC is also required.
Example: Class 3.1A and 3.1B substances in open and closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 1 x 20 L of Substance A (class 3.1B) in an open container
- 1 x 20 L of Substance B (class 3.1B) in a closed container
- 5 x 2 L of Substance C (class 3.1B) in closed containers
- 5 x 20 L of Substance D (class 3.1C) in closed containers
- 2 x 100 L of Substance E (class 3.1C) in open containers.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
| Classification | Total amount held | Threshold (HSL)* | Ratio |
| 3.1B | 20 L | 50 L (in open containers) | 0.4 (20/50) |
| 3.1B | 20 L | 100 L (in closed containers more than 5 L) | 0.2 (20/100) |
| 3.1B | 10 L (2 x 5 L) | 250 L (in closed containers up to 5 L) | 0.04 (10/250) |
| 3.1C | 100 L (5 x 20 L) | 500 L (in closed containers more than 5 L) | 0.2 (100/500) |
| 3.1C | 200 L (2 x 100 L) | 250 L (in open containers) | 0.8 (200/250) |
| QRS | 1.64 |
* From Table 4 Schedule 9: Quantities of classes 2–4 substances that activate HSL requirements(external link)
For classes 1–5, substances of the same subclass are added together. As the QRS is greater than 1 (1.64), the HSL threshold has been exceeded and the workplace requires an HSL. An LCC is also required.
Example: Class 3.1A-D substances in closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 1 x 10 L of Substance A (not petrol, aviation gasoline or racing gasoline) (class 3.1A) in a closed container
- 20 x 5 L of Substance C (class 3.1B) in closed containers
- 100 x 5 L of Substance D (class 3.1C) in closed containers
- 1 x 1000 L of Substance E (class 3.1D) in a closed container.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
| Classification | Total amount held | Threshold (HSL)* | Ratio |
| 3.1A (not petrol, aviation gasoline, and racing gasoline) | 10 L (1 x 10 L) | 20 L (in open or closed container) | 0.5 (10/20) |
| 3.1B | 100 L (20 x 5 L) | 250 L (in closed containers up to 5 L) | 0.4 (100/250) |
| 3.1C | 500 L (100 x 5 L) | 1,500 L (in closed containers up to 5 L) | 0.33 (500/1500) |
| 3.1D | 1000 L (1 x 1000 L) | No threshold | Not applicable |
| QRS | 1.23 |
* From Table 4 Schedule 9: Quantities of classes 2–4 substances that activate HSL requirements(external link)
The 3.1D substance does not need to be included in the calculation as 3.1D does not trigger an HSL or LCC requirement (Table 1).
For classes 1–5, substances of the same subclass are added together. As the QRS is greater than 1 (1.23), the HSL threshold has been exceeded and the site requires an HSL. An LCC is also required.
Example: Class 3.1B and 3.1C substances in closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 10 x 20 L of Substance A (class 3.1B) in closed containers
- 2 x 100 L of Substance C (class 3.1C) in closed containers.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
| Classification | Amount held | Threshold* | Ratio |
| 3.1B | 200 L (10 x 20 L) | 100 L (in closed containers more than 5 L) | 0.5 |
| 3.1C | 200 L (2 x 100 L) | 500 L (in closed containers more than 5 L) | 0.4 |
| QRS | 0.9 |
* From Table 4 Schedule 9: Quantities of classes 2–4 substances that activate HSL requirements(external link)
As the QRS is less than 1 (0.9), the HSL threshold has not been exceeded and the workplace does not require an HSL.
Example: Area with substances that are Class 3 and Class 6
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 10 x 20 L containers of acetonitrile (a 3.1B and 6.1B substance) in closed containers in storage.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
- The threshold quantity for a 3.1B substance in closed containers more than 5 L is 100 L (From Table 4 Schedule 9: Quantities of classes 2-4 substances that activate HSL requirements(external link)).
- The threshold quantity for a 6.1B substance in storage is 250 L.
| Substance | Classification | Amount held | Threshold (for an HSL) | Ratio |
| Acetonitrile | 3.1B and 6.1B | 200 L (10 x 20 L) |
3.1B – 100 L (in closed containers) 6.1B – 250 L |
For 3.1 = 2 (200 L /100 L) For 6.1B = 0.8 (200 L/250 L) |
| QRS for 3.1 | 2 | |||
| QRS for 6.1 | 0.8 |
As the QRS for class 3.1 is greater than 1 (2), the HSL threshold has been exceeded and the area where the acetonitrile is stored requires an HSL for class 3.1.
As the QRS for class 6.1 is less than 1 (0.8), the HSL threshold has not been exceeded and the area where the acetonitrile is stored does not require an HSL for class 6.1.
Examples of the QRS calculations with class 5 substances
Example: Class 5.1.1 substances that are being used or kept in packages that are closed at all times
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has class 5.1.1 substances that are being used or kept in packages that are closed at all times.
The area within the workplace has:
- 1 L of Substance A (class 5.1.1A) being used
- 20 L of Substance B (class 5.1.1B) being used
- 200 kg of Substance C (class 5.1.1B) kept in a closed container at all times
- 20 L of Substance D (class 5.1.1C) being used
- 400 kg of Substance E (class 5.1.1C) kept in a closed container at all times.
Regulation 12.8 sets out a PCBU’s duty to establish an HSL for class 5.1.1 substances(external link)
| Classification | Amount held | Threshold* | Ratio |
| 5.1.1A | 1 L | 5 L (substance being used) | 0.2 (1/5) |
| 5.1.1B | 20 L | 50 L (substance being used) | 0.4 (20/50) |
| 5.1.1B | 200 kg | 500 kg (in closed containers) | 0.4 (200/500) |
| 5.1.1C | 20 L | 100 L (substance being used) | 0.2 (20/100) |
| 5.1.1C | 400 kg | 1000 kg (in closed containers) | 0.4 (400/1000) |
| QRS for 5.1.1 (kept in closed container at all times) | 0.8 (0.4 + 0.4) | ||
| QRS for 5.1.1 (being used) | 0.8 (0.2 + 0.4 + 0.2) |
* From Tables 1 and 2 Schedule 10: Quantities of classes 5.1.1 and 5.1.2 that activate HSL requirements(external link)
For classes 1–5, substances of the same subclass are added together. However, class 5.1.1 substances to be ‘manufactured or used’ and substances ‘in packages that are closed at all times’ must be stored at separate HSLs (regulation 12.8 (2)(external link)). This means the QRS values for these are not added together. This also applies to class 5.1.2 and 5.2 substances.
As the QRS values are less than 1 (0.8), the HSL threshold has not been exceeded and the workplace does not require an HSL or LCC.
The LCC thresholds for class 5.1.1 substances are not the same as for HSLs. Regulation 12.17(external link) sets out a PCBU’s duty to establish an LCC for class 5.1.1 substances. They apply to all class 5.1.1 substances, whether they are in closed packages or are being manufactured or used.
Example: Class 5.1.1 substances that are being used
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 40 kg of Substance A (class 5.1.1B) being used
- 50 kg of Substance B (class 5.1.1C) being used.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
- The threshold quantity for a 5.1.1B substance where manufactured or used is 50 kg.
- The threshold quantity for a 5.1.1C substance where manufactured or used is 100 kg.
| Classification | Amount held | Threshold (for an HSL) | Ratio |
| 5.1.1B | 40 kg | 50 kg (in use) | 0.8 (40/50) |
| 5.1.1C | 50 kg | 100 kg (in use) | 0.5 (50/100) |
| QRS for 5.1.1 HSL | 1.3 (0.8 + 0.5) | ||
As the QRS for 5.1.1 is greater than 1 (1.3), the HSL threshold has been exceeded and the area where the substances are used requires an HSL for class 5.1.1.
| Classification | Amount held | Threshold (for an LCC) | Ratio |
| 5.1.1B | 40 kg | 500 kg (in use) | 0.08 (40/500) |
| 5.1.1C | 50 kg | 1000 kg (in use) | 0.05 (50/1000) |
| QRS for 5.1.1 LCC | 0.13 (0.08 + 0.05) | ||
However, the threshold for requiring a LCC for class 5.1.1 substances in use is 10 x higher than the HSL threshold for class 5.1.1. In this example, an LCC is not required.
Example: Substances that are Class 5.1.1 and Class 8.2
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has:
- 1 x 1000 kg container of chromium trioxide (a 5.1.1B and 8.2B substance) in a closed container in storage.
Regulation 10.26 sets a PCBU’s duty to establish an HSL for class 3 substances(external link)
- The threshold quantity for a 5.1.1B substance in closed containers is 500 kg.
- The threshold quantity for an 8.2B substance in storage is 250 kg.
| Substance | Classification | Amount held | Threshold (for an HSL) | Ratio |
| Chromium oxide | 5.1.1B and 8.2B | 1000 kg |
5.1.1B – 500 kg (in closed containers) 8.2B – 250 kg |
For 5.1.1 = 2 (200 kg /100 kg) For 8.2B = 4 (1000 kg/250 kg) |
| QRS for 5.1.1 | 2 | |||
| QRS for 8.2 | 2 | |||
As the QRS for 5.1.1 is greater than 1 (2), the HSL threshold has been exceeded and the area where the chromium oxide is stored requires an HSL for class 5.1.1.
As the QRS for 8.2 is greater than 1 (4), the HSL threshold has been exceeded and the area where the chromium oxide is stored also requires an HSL for class 8.2.
This means the requirements for both 5.1.1B and 8.2B need to be met.
Example: Class 5 substances kept in closed containers at all times
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has:
- 150 kg of Substance A (class 5.1.1B) kept in a closed container at all times
- 300 kg of Substance B (class 5.1.1C) kept in a closed container at all times
- 50 kg of Substance C (class 5.1.2A) – non-permanent gas kept in a closed container at all times
- 0.5 kg of Substance D (class 5.2B) kept in a closed container at all times
- 8 kg of Substance E (class 5.2D) kept in a closed container at all times.
Regulation 12.34 sets out a PCBU’s duty to establish an HSL for class 5.2 substances(external link)
| Classification | Amount held | Threshold* | Ratio |
| 5.1.1B | 150 kg | 500 kg (in closed containers) | 0.3 (150/500) |
| 5.1.1C | 300 kg | 1000 kg (in closed containers) | 0.3 (300/1000) |
| 5.1.2A | 50 kg | 100 kg (non-permanent gas in closed containers) | 0.5 (50/100) |
| 5.2B | 0.5 kg | More than 1 kg | 0.5 (0.5/1) |
| 5.2D | 8 kg | More than 10 kg | 0.8 (8/10) |
| QRS for 5.1.1 | 0.6 (0.3 + 0.3) | ||
| QRS for 5.1.2 | 0.5 | ||
| QRS for 5.2 | 1.3 (0.5 + 0.8) | ||
* From Tables 1 and 2 Schedule 10: Quantities of classes 5.1.1 and 5.1.2 that activate HSL requirements(external link)
From Table 1 Schedule 11: Quantities of class 5.2 that activate HSL requirements(external link)
For classes 1–5, substances of the same subclass are added together.
The QRS for the class 5.1.1 substances are added together as both the 5.1.1B and 5.1.1C substances are kept in closed containers at all times and so could be kept together (see previous example for explanation).
As the QRS for class 5.2 substances is greater than 1 (1.3), the HSL threshold has been exceeded and an HSL needs to be established for the class 5.2 substances but not for the 5.1.1 and 5.1.2 substances.
Class 5.1.1, 5.1.2 and 5.2 substances are all incompatible with each other so should not be stored together.
Example of the QRS calculations for class 5.1.2 gases
Example: Class 5.1.2A gases
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace has:
- 145.5 m³ oxygen – permanent gas
- 71 kg chlorine – non-permanent gas.
| Classification | Amount held | Threshold* | Ratio |
| 5.1.2A oxygen | 145.5 m³ | 200 m³ | 0.725 (145.5/200) |
| 5.1.2A chlorine | 71 kg | 150 kg | 0.473 (71/150) |
| QRS | 1.198 (0.725 + 0.473) | ||
* From Tables 1 and 2 Schedule 10: Quantities of classes 5.1.1 and 5.1.2 that activate HSL requirements(external link)
For classes 1–5, substances of the same subclass are added together. The QRS for permanent and non-permanent gases of the same subclass can be added together.
As the QRS is greater than 1 (1.198), the HSL threshold has been exceeded and the workplace requires an HSL.
More about permanent and non-permanent gases
Permanent and non-permanent gases have separate thresholds as they are measured in different units. A ‘permanent gas’ means a gas with a critical temperature not exceeding –50°C.
A permanent gas is measured in m³ and a non-permanent gas in kg.
Regulation 10(5) provides:
Where a quantity of gas is specified:
- as cubic metres (m³), this volume is determined by taking the contents and conditions of the gas held in a container and then calculating the volume that the gas would occupy at 15°C and 101.3 kPa absolute pressure:
- in kilograms (kg), this refers to the net weight of the gas in liquefied form as held in its container.
Calculations for all containers including cylinders should use the quantity of full containers as this is the maximum amount that might be in the workplace.
Class 6 or 8 gases do not have HSL or LCC requirements. Regulation 13.38(external link) only includes solids and liquids that are stored.
Example of the QRS calculations for class 3 and class 5 substances
Where substances are incompatible they should be segregated and stored at separate HSLs, so they should not be added together when calculating the QRS.
Example: Class 3 and 5 substances in closed containers
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has:
- 20 x 5 L of Substance A (class 3.1B) in closed containers
- 100 x 5 L of Substance B (class 3.1C) in closed containers
- 1 x 150 L of Substance C (class 5.1.1B) kept in a closed container at all times
- 1 x 300 L of Substance D (class 5.1.1C) kept in a closed container at all times.
Regulation 10.26 sets out a PCBU’s duty to establish an HSL for class 3 substances(external link)
Regulation 12.8 sets out a PCBU’s duty to establish an HSL for class 5.1.1 substances(external link)
Regulation 12.17 sets out the criteria for an LCC for class 5.1.1 substances(external link)
| Classification | Amount held | Threshold* | Ratio |
| 3.1B | 100 L (20 x 5 L) | 250 L (in closed containers up to 5L) | 0.4 (100/250) |
| 3.1C | 500 L (100 x 5 L) | 1500 L (in closed containers up to 5L) | 0.33 (500/1500) |
| 5.1.1B | 150 L (1 x 150 L) | 500 L (in closed containers) | 0.3 (150/500) |
| 5.1.1C | 300 L (1 x 300 L) | 1000 L (in closed containers) | 0.3 (300/1000) |
| QRS for 3.1 | 0.73 (0.4 + 0.33) | ||
| QRS for 5.1.1 | 0.6 (0.3 + 0.3) | ||
* From Table 4 Schedule 9: Quantities of classes 2–4 substances that activate HSL requirements(external link) From Table 1 Schedule 10: Quantities of classes 5.1.1 and 5.1.2 that activate HSL requirements(external link)
Subclasses 3.1 and 5.1.1 are not added together. For class 1 to 5, only substances of the same subclass are added together.
As the QRS is less than 1 (0.9), the HSL threshold has not been exceeded for class 3.1 or class 5.1.1. The workplace does not require any HSLs or LCCs.
Examples of the QRS calculations for class 6 and 8 substances
Example: Class 6 and 8 substances in storage with no incompatible substances
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The area within the workplace stores:
- 100 L of Substance A (class 6.1B)
- 400 kg of Substance B (class 6.1C)
- 100 L of Substance C (class 8.2B).
| Classification | Amount held | Threshold (from regulation 13.38(external link)) | Ratio |
| 6.1B | 100 L | 250 L | 0.4 (100/250) |
| 6.1C | 400 kg | 1000 kg | 0.4 (400/1000) |
| 8.2B | 100 L | 250 L | 0.4 (100/250) |
| QRS | 1.2 | ||
The ratios for class 6 and 8 substances (no incompatible substances) can be added together. As the QRS is greater than 1 (1.2), the HSL threshold has been exceeded and the workplace requires an HSL. HSL and LCC thresholds are the same for class 6 and 8 substances. Note there are threshold variations for class 6 and 8 for a farm >4ha.
HSLs for class 6 and 8 substances are only required for substances in storage. For more information see WorkSafe's website
Example: Class 6 and 8 substances stored with incompatible substances (acid/alkali)
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has:
- 100 L of Substance A (class 6.1B)
- 400 kg of Substance B (class 6.1C)
- 50 L of Substance C (class 8.2B alkali) – incompatible with acid
- 50 L of Substance D (class 8.2B acid) – incompatible with alkali.
| Classification | Amount held | Threshold (From regulation 13.38(external link)) | Ratio |
| 6.1B | 100 L | 250 L | 0.4 (100/250) |
| 6.1C | 400 kg | 1000 kg | 0.4 (400/1000) |
| 8.2B alkali (incompatible with acid) | 50 L | 250 L | 0.2 (50/250) |
| 8.2B acid (incompatible with alkali) | 50 L | 250 L | 0.2 (50/250) |
| QRS for 8.2B stored with 6.1B and 6.1C | 1 (0.4 + 0.4 + 0.2) | ||
| QRS for 8.2B stored separately | 0.2 | ||
The acid and alkali must not be stored in the same HSL as they are incompatible. Their ratios are not added together.
If one of the class 8.2B substances is stored with 6.1B and 6.1C substances, the ratios are added together.
As the QRS values are 1 and less than 1 (0.2), the HSL threshold has not been exceeded and the workplace does not require an HSL.
Example: Class 6 and 8 substances stored with incompatible substances (acid/cyanide)
The PCBU wants to know if they need to establish any hazardous substance locations at their workplace.
The workplace has:
- 20 kg of cyanide (class 6.1A)
- 300 L of Substance B (class 6.1C)
- 100 L of Substance C (class 8.2B acid) – incompatible with cyanide.
| Classification | Amount held | Threshold (From regulation 13.38(external link)) | Ratio |
| 6.1A cyanide | 20 kg | 50 kg | 0.4 (20/50) |
| 6.1C | 300 L | 1000 L | 0.3 (300/1000) |
| 8.2B acid (incompatible with cyanide) | 100 L | 250 L | 0.4 (100/250) |
| QRS for 6.1A and 6.1C | 0.7 (0.4 + 0.3) | ||
| QRS for 8.2B acid stored separately | 0.4 | ||
As the class 8.2B acid is incompatible with the 6.1A cyanide, these substances must be stored separately. The QRS for the class 8.2B acid is not added to the QRS for the class 6.1 substances.
As the QRS values are less than 1 (0.7 and 0.4), the HSL threshold has not been exceeded and the workplace does not require an HSL.
Appendices
Appendix 1: Explanation of pre-30 April 2021 HSNO classes
The Hazardous Substances (Classification) Notice 2017, issued under the HSNO Act, established a system for classifying hazardous substances covered by the Health and Safety at Work Regulations. This system consists of three components:
- Numbered Classes: These classes (for example, class 3, class 6) indicate the inherent hazardous properties of a substance.
- Numbered Subclasses: These subclasses (for example, subclass 3.1, subclass 6.1) specify the type of hazard posed by a substance.
- Lettered Categories: These categories (for example, category A) indicate the severity of the hazard posed by a substance.
The hazardous properties of a substance are classified to determine how the risks can be managed. There are eight key hazard classes:
- Class 1: explosives
- Class 2: flammable gases
- Class 3: flammable liquids
- Class 4: flammable solids
- Class 5: oxidising substances
- Class 6: substances toxic to people
- Class 8: corrosive substances
- Class 9: substances toxic to the environment.
The hazard classification of a substance is determined by combining the numbers and letters from these three components. For example, 3.1A is a hazard classification.
Notes
- This 2017 EPA notice has been superseded, and the HSNO Act now utilises the GHS categories for classifying substances.
- Despite the existence of a newer Hazard Classification Notice, the HS Regulations still adhere to the classification system outlined in the 2017 Notice.
- SDSs must use GHS after April 30, 2025. PCBUs may still have pre-30 April 2021 HSNO classifications for substances supplied before this date.
In cases where the safety data sheet includes GHS categories, these must be converted to the pre-30 April 2021 HSNO classification using the correlation table provided in Schedule 3 of the Hazardous Substances (Hazard Classification) Notice 2020(external link)
Appendix 2: Regulation 10 of the Hazardous Substances Regulations
Regulation 10: References to quantities
- In determining whether the requirement for a hazardous substance location or a compliance certificate is activated, the threshold quantity is exceeded if the quantity ratio sum is greater than 1 when determined in accordance with the following formula:
quantity ratio sum = Σ [qpi/qai]
where:- Σ is the symbol for summation of the calculated ratios for all the hazard classifications present
- qpi is the quantity of substance with a particular hazard classification present
- qai is the quantity of substance of that hazard classification that activates the relevant requirement.
- The quantity ratio sum for class 1 to 5 substances must:
- sum only substances of the same subclass (for example, class 3.1A, 3.1B, and 3.1C substances), and
- include only those classes that trigger the requirement.
- The threshold quantity ratio sum for class 6 and 8 substances must include both classes unless the substances are incompatible with each other as described in Schedule 15 and are stored separately.
- Unless otherwise specified, the quantity of an organic peroxide must be determined by mass.
- Where a quantity of gas is specified:
- as cubic metres (m³), this volume is determined by taking the contents and conditions of the gas held in a container and then calculating the volume that the gas would occupy at 15°C and 101.3 kPa absolute pressure
- in kilograms (kg), this refers to the net weight of the gas in liquefied form as held in its container.
- Where a quantity refers to a class 1 substance, that quantity must be a net explosive quantity (NEQ), where NEQ is the gross weight less the weight of any construction materials of the article in kilograms (kg).
Appendix 3: Regulations where QRS is used to determine if the requirement applies
| Regulation | Requirement | Classification | Threshold reference |
| 10.26(external link) | Duty of PCBU to establish hazardous substance location – for class 2, 3 and 4 | 2.1.1A, 2.1.1B, 2.1.2A 3.1A, 3.1B, 3.1C 3.2A, 3.2B, 3.2C 4.1.1A, 4.1.1B 4.1.2A, 4.1.2B, 4.1.2C, 4.1.2D, 4.1.2E, 4.1.2F, 4.1.2G 4.1.3A, 4.1.3B, 4.1.3C 4.2A, 4.2B, 4.2C 4.3A, 4.3B, 4.3C |
Table 4 Schedule 9(external link) |
| 10.34(external link) | Requirement to have compliance certificate if class 2.1.1, 2.1.2, or 3.1 substance present at hazardous substance location | 2.1.1A, 2.1.1B 2.1.2A 3.1A, 3.1B, 3.1C |
Table 4 Schedule 9(external link) |
| 10.36(external link) | Requirement to have compliance certificate if class 3.2 or 4 substance present at hazardous substance location | 3.2A, 3.2B, 3.2C 4.1.1A, 4.1.1B 4.1.2A, 4.1.2B, 4.1.2C, 4.1.2D, 4.1.2E, 4.1.2F, 4.1.2G 4.1.3A, 4.1.3B, 4.1.3C 4.2A, 4.2B, 4.2C 4.3A, 4.3B, 4.3C |
Table 4 Schedule 9(external link) |
| 12.8(external link) | Duty of PCBU to establish hazardous substance location where class 5.1.1 and 5.1.2 substances present | 5.1.1A, 5.1.1B, 5.1.1C 5.1.2A |
Table 1 and 2 Schedule 10(external link) |
| 12.17(external link) | Requirement to have compliance certificate for hazardous substance location – for class 5.1.1 and 5.1.2 | 5.1.1A, 5.1.1B, 5.1.1C 5.1.2A |
Regulation 12.17(external link) |
| 12.34(external link) | Duty of PCBU to establish hazardous substance location where class 5.2 substance present Table 1 Schedule 11 | 5.2A, 5.2B, 5.2C, 5.2D, 5.2E, 5.2F | Table 1 Schedule 11(external link) |
| 12.42(external link) | Requirement to have compliance certificate for hazardous substance location – for class 5.2 | 5.2A, 5.2B, 5.2C, 5.2D, 5.2E, 5.2F | Regulation 12.42(external link) |
| 13.34(external link) | Duty of PCBU to establish hazardous substance location where certain class 6 or 8 substances present | 6.1A, 6.1B, 6.1C 8.2A, 8.2B |
Regulation 13.38(external link) |
| 13.38(external link) | Compliance certificate required for hazardous substance location – for class 6.1 and 8.2 | 6.1A, 6.1B, 6.1C 8.2A, 8.2B |
Regulation 13.38(external link) |
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