Class 4.3 Dangerous When Wet Sign

Class 4.3 Dangerous When Wet Sign

Class 4.3 Dangerous When Wet Sign – The ‘Class 4 Dangerous When Wet Sign’ helps to protect the health and safety of staff. The symbol in Sign clearly warns of hazards that could easily lead to injury and accident. Dangerous when wet substance means a material that, by contact with water. Is liable to become spontaneously flammable or to give off flammable or toxic gas at a rate greater than 1 litre per kilogram of the material, per hour. For example Sodium, Potassium, and Lithium hydride.

The Class 4.3 Dangerous When Wet Sign are used for areas where dangerous goods are transported or may be stored. The ‘Class 4.3 Dangerous When Wet Sign’ features a flame symbol above the words dangerous when wet followed by a large, bold number 4.3. The sign comprises a blue background with white wording and symbols.

Note on 120 mm size: The 120 mm option is not compliant for transport placards, as NZ regulations require a minimum of 250 mm per side for vehicle use. However, it is very useful for small-scale applications such as cylinder cages, storage cabinets, and indoor warning signage where space is limited.

Note on larger sizes (400 mm – 800 mm): While 250 mm is the minimum required size for transport placards, larger signs (400 mm, 600 mm, 800 mm) are recommended for warehouses, depots, bulk storage areas, and outdoor use. The extra size improves long-distance visibility and makes hazards clear to staff, visitors, and emergency responders.

“Before you spark up that reaction, see how Class 4 materials rate on our Dangerous Goods Class Guide. It’s solid advice.”

What’s the difference between the signs with a class number (e.g. 4.3) and the ones without?

• Signs that include the class number (e.g. 4.3, 2.1, 8) are part of the UN Dangerous Goods system. These are mandatory for transport and bulk storage. You’ll see them on trucks, shipping containers, depots, and outdoor storage facilities.

• Signs that do not include the class number are part of the GHS workplace labelling system. These are typically used on containers, cabinets, cylinder cages, and indoor workplaces where hazardous substances are handled but not being transported.

FAQ

1. What does a Class 4.3 Dangerous When Wet Sign mean?
   It indicates substances that react dangerously with water, releasing flammable gases or causing explosions.

2. Where should Class 4.3 Signs be displayed?
   They must be displayed on vehicles, depots, and storage areas handling water-reactive substances in line with NZ and AU dangerous goods regulations.

3. What size sign do I need?
   Transport placards must be 250 mm minimum. Smaller 120 mm are useful for lab or cage storage, while larger 400–800 mm options are ideal for depots and outdoor placement.

Classifications:

General guide as specified by WorksafeNZ: Properties of hazardous substances have been classified so to determine the best way the risks can be managed. They have been classified into eight key hazard classes:

•  1: Explosives.
•  2: Flammable gases.
•  3: Flammable liquids.
•  4: Flammable solids.
•  5: Oxidising substances.
•  6: Substances toxic to people.
•  8: Corrosive substances.
•  9: Substances toxic to the environment.

How to choose the right mounting options.

Corflute: short term less than 2 years outdoors

Thin PVC: Medium term, more than 2 years

ACM: Long term 5 years or more

Supplied as a sticker:

long term digital print laminated for long term use. With a life of 5 years or more. We use a Hi Tac vinyl which allows it to be applied most surfaces.

Magnetic mounting option for the Class 4.3 Dangerous When Wet Sign

Flexible, vehicle-grade magnetic placards with the Class 4.3 Dangerous When Wet Sign printed on premium vinyl, laminated, and mounted to automotive magnetic sheeting. They stick to ferrous steel panels and remove without residue—ideal for vehicles that only carry DG sometimes.

Who they’re for

• Contractors / couriers who transport Dangerous Goods occasionally

• Hire or multi-use vehicles (no permanent signage)

• Sites that swap classes depending on load (quick changeover)

• Size: 250 × 250 mm (meets common road minimums).

• Magnet: vehicle-grade sheet, 0.8–1.0 mm thick (30–40 mil), high-energy.

• Face film: outdoor self-adhesive vinyl + UV laminate (gloss).

• Operating temp: suitable from winter cold to summer heat (typical automotive range).

• Print: high-contrast blue/white artwork.

Where they work (and don’t)

• Works on: painted steel panels that are flat, clean, and smooth.

• Doesn’t work on: aluminium, stainless, plastics, composites, heavy body filler; vinyl wraps, ceramic coatings, heavily textured paint.

• If customers have aluminium doors/ute trays, suggest self-adhesive or rigid ACM instead.

Fitment checklist

1. Clean & dry the panel (no wax/polish).

2. Warm, flat magnet—no curl.

3. Apply to flat steel only; press from centre out.

4. Do not bridge panel gaps, ribs or sharp curves.

5. Remove daily to clean/dry both surfaces; store flat.

6. In heavy rain/highway speeds, check edges haven’t lifted.

Care & maintenance

• Remove and wipe after wet weather; store flat (never rolled tight).

• Move position slightly each week to avoid differential fading.

• Avoid use on freshly resprayed paint (allow full cure).

Compliance note

• Magnet is a mounting method. The operator must ensure placards are the correct class, size, and securely affixed for the journey. Some carriers or site rules may require permanent/rigid placards—check your procedure.

For more information check out these links

• WorkSafe NZ – Hazardous Substances Management
  👉 WorkSafe NZ – Hazardous substances

• EPA NZ – HSNO Act guidance
  👉 EPA NZ – Hazardous Substances and New Organisms (HSNO) Act

• United Nations GHS
  👉 UN – Globally Harmonized System (GHS)  

• Why you need the correct Hazard sign

Check out our: Complete Guide to Dangerous Goods Placards (NZ & AU)

Why you need the correct Hazard sign

NZS/AS 1319:1994 advocates simplicity and clarity in safety signage. To be effective, they should be easy to read and interpret at a glance.

The Standard is about the use of legible text and appropriate, simple symbols.

By simplifying the message, it reduces the risk of misinterpretation, which increases the chances of the sign’s warning or instruction being followed.

Enhancing the signs visibility through placement and colour

Placement and visibility will play a crucial role in the efficiency of safety signs.

The standard states that signs must be positioned near the hazard they are warning about, which ensures that the safety message is relevant. Also it advocates the use of contrasting colours for the background and lettering. This attention to the colour scheme will increase visibility and readability from a reasonable distance, which ensures the message is accessible.

The mission of Hazard Signs NZ is to provide quality-made safety signs to all of New Zealand. Our great prices and convenient online ordering platform make us a preferred supplier to many NZ businesses. All our signs are designed and manufactured in Invercargill to meet the workplace health and safety needs of all businesses and industries in New Zealand.

Please note. We make some of our safety signs to order and it may take 5 to 10 business days to receive. If you require your order urgently, please don’t hesitate to contact us to confirm an estimated delivery date prior to placing your order.

If you are not sure about what sign you need for your business, just contact us at +6432183350 or email us and we will make it ready for you.