Class 4.3 Dangerous When Wet 3170 Hazardous Sign

Hazardous Sign – Class 4.3 Dangerous When Wet 3170 Hazardous Sign

Class 4.3 Dangerous When Wet 3170 Hazardous Sign – is used to mark hazardous areas in the building and around it. The ‘Class 4.3 Dangerous When Wet 3170 Hazardous Sign’ is used in those places where dangerous goods are being shipped or may be stored. This ‘Class 4.3 Dangerous When Wet 3170 Hazardous Sign’ depicts a symbol of fire above the “Dangerous When Wet” words accompanied by a big, bold number 3170 and 4.3 that indicates the bulk presence of Aluminium Smelting By-Products.

Comparison with Other Class 4 Dangerous Goods

Class 4.1 – Flammable Solids

• Includes materials that ignite easily when exposed to heat, sparks, or friction (e.g., matches, nitrocellulose).

• Sign colour: Red with flame symbol.

• Key risk: fire hazard from ignition.

Class 4.2 – Spontaneously Combustible

• Covers substances that ignite on contact with air (e.g., phosphorus, pyrophoric metals).

• Sign colour: Half red/half white with flame symbol.

• Key risk: self-ignition without external heat source.

Class 4.3 – Dangerous When Wet (this product)

• Includes materials that react dangerously with water, producing flammable gases or explosive conditions (e.g., calcium carbide, sodium metal, UN 3170 substances).

• Sign colour: Blue with flame symbol.

• Key risk: explosive or toxic gas release when in contact with moisture.

What does “UN 3170” mean?

• UN 3170 is the official United Nations number assigned to “Aluminium Alkyls, Dangerous When Wet” and other substances in the same group.

• It indicates that these materials are part of Class 4.3 Dangerous Goods — substances that react dangerously with water to release flammable gases.

• UN numbers are used globally in transport documentation, vehicle placards, and workplace signage to ensure emergency services instantly know the hazard type.

• In this case, “3170” helps fire crews and hazmat responders recognise that the cargo poses a risk of explosive or toxic gas release if it comes into contact with moisture.

FAQ

Q1: Why do I need a Class 4.3 Dangerous When Wet sign?
This sign is required by NZS 5433:2020 and international UN Model Regulations to identify substances that react dangerously with water. It ensures compliance and helps emergency services respond safely.

Q2: Where should this sign be used?
It must be displayed on vehicles transporting Class 4.3 goods, storage tanks, warehouses, and entry points to facilities storing these hazardous materials.

Q3: What does the blue diamond symbol mean?
The blue background with flame symbol identifies water-reactive substances. It clearly warns that even small amounts of water contact may cause fire, explosion, or toxic gas release.

The Class 4.3 “Dangerous When Wet” sign warns that the substance reacts violently with water — releasing flammable gases or causing fire or explosion.
It’s critical for materials like aluminium phosphide or magnesium powder, which must be kept completely dry.
Learn about all DG classes and their risks in Understanding Dangerous Goods Classes 1–9.

The UN number 3170 identifies “Aluminium Smelting Byproducts,” which may release hydrogen gas when wet.
Understanding UN numbers and their emergency response codes is covered in Understanding HAZCHEM Signs in New Zealand & Australia.

For large storage areas or bulk transport of Class 4.3 materials, an EIP showing the UN number and emergency code is mandatory.
Learn more about how and where to use these in Emergency Information Panel Signs Explained.

Got stuff that goes “boom” when it gets wet? That’s one barbecue you don’t want to host!
Match it with our Aluminium Smelting Byproducts Sign — perfect for sites handling reactive residues.

How to choose the right mounting options.

Corflute: short-term 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 to most surfaces.

Magnetic mounting option for the Class 4.3 Dangerous When Wet 3170 Hazardous Sign

Flexible, vehicle-grade magnetic placards with the Class 4.3 Dangerous When Wet 3170 Hazardous 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)

• 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).

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

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.