Worksite fence displaying No Entry Authorised Persons Only Prohibition Sign

Know the Difference: Mandatory Signs and Prohibition Signs Unpacked

In Australia, workplace safety isn’t just good practice — it’s law. From construction sites and warehouses to hospitals and offices, the use of correct safety signage is critical to maintaining compliance with Australian Standard AS 1319-1994 and ensuring everyone goes home safe. Two of the most common and essential types of safety signage you’ll encounter are Mandatory Signs and Prohibition Signs. Both serve important roles in communicating workplace safety, but their purposes, designs, and messages differ significantly. Understanding these differences is key to creating a safer environment.

In this guide, we’ll break down the key distinctions between Mandatory Signage and Prohibition Signage, and why getting them right is crucial for any Australian workplace.

Why Clear Safety Signage Matters in Australian Workplaces

Australian workplaces operate under stringent health and safety standards. AS 1319-1994 – Safety Signs for the Occupational Environment outlines how safety signage should be used to communicate risks, required actions, and prohibited behaviours. Clear, well-placed signage is a frontline defence against injuries, particularly in high-risk environments like manufacturing plants, construction zones, or laboratories. When seconds matter, the right sign makes the difference between someone stopping to think — or stepping straight into danger.

Mandatory Signs and Prohibition Signs each play distinct roles in creating a safe environment. Understanding their differences is the first step toward using them effectively and ensuring that safety is never compromised.

Mandatory Signs — What You Must Do

Design Features of Mandatory Signs

Mandatory signs follow a strict design to ensure they are instantly recognisable. In Australia, Mandatory Safety Signage typically features:

  • A blue circular background

  • A white symbol or pictogram clearly illustrating the required action

  • Sometimes, black text on a white background is added for clarity

  • Strong language like “MUST” is often used to remove any ambiguity

These signs are not polite suggestions — they are instructions that must be followed for safety or legal compliance.

Purpose of Mandatory Signs

Mandatory Signs tell workers, visitors, and contractors exactly what they are required to do. Their primary purpose is to prevent injury and enforce safety protocols. Think of them as the non-negotiable rules of the workplace. Ignoring a mandatory sign could put yourself or others at risk — and may land the business in breach of safety regulations.

Common Examples:

These are typical examples of Mandatory PPE Signs — directing workers to wear personal protective equipment (PPE) necessary to mitigate specific workplace risks.

Prohibition Signs — What You Cannot Do

Design Features of Prohibition Signage

Just as Mandatory Signs are easy to spot, Prohibition Signs uses universal "stop" cues designed to grab attention and instantly communicate a restriction. Their design includes:

  • A white background

  • A red circular border with a diagonal red slash running through it

  • A black pictogram showing the action being banned

  • Optional black text below or beside the image for added clarity

The red slash is unmistakable. It means, quite simply: Don’t do this.

Purpose of Prohibition Signs

Prohibition Signs are about preventing dangerous or unauthorised behaviours in specific areas. They exist to protect both the individual and the wider workplace community from harm. These signs are clear and simple, telling workers exactly what actions are prohibited in certain areas to avoid accidents or legal violations.

Common Examples:

These are examples of a Prohibition Sign that outlines activities that should not occur under any circumstances. They help ensure that unsafe or unauthorised actions don’t happen in hazardous zones.

Key Differences Between Mandatory Signs and Prohibition Signs

While both Mandatory Signs and Prohibition Signs aim to improve safety, they’re opposites in both design and purpose. Here’s a breakdown of the key distinctions:

1. Colour Scheme

The colour palette is your first clue.

  • Mandatory Signs: Blue and white dominate

  • Prohibition Signs: Red, white, and black grab attention

The colour difference helps workers make a quick judgement — is this something I need to do, or something I must not do?

2. Message Intent and Tone

  • Mandatory Signs: Provide clear instructions for what is required

  • Prohibition Signs: Lay down the law on what is forbidden

Mandatory Signs are about action — "Do this." Prohibition Signs are about restriction — "Stop. You can’t do this."

3. Visual Symbols and Wording

  • Mandatory: Blue circle + white action symbol. Often uses the word “MUST”.

  • Prohibition: Red circle with a diagonal slash + black symbol. Text often includes “NO” or “NOT PERMITTED”.

The difference in design ensures that the message is understood at a glance, even in noisy or chaotic environments.

Why Getting This Right Matters — Compliance and Safety in Australia

Using the correct signage isn’t just good practice; it’s enforceable under Australian safety laws. AS 1319-1994 exists to prevent confusion and ensure that everyone understands what’s expected of them — instantly.

The Risks of Mixing Them Up:

  • Legal penalties for non-compliance

  • Confusion leading to unsafe behaviours

  • Reduced credibility of the safety messaging

  • Increased risk of injury or incidents

Clear signage prevents that moment of hesitation where someone thinks, "Can I do this?" or "Do I really have to?" With the right sign, the answer is obvious.

For employers, investing in properly designed Mandatory Signage and Prohibition Signage is a legal obligation and a moral one. It shows you value the safety of your people — and that matters.

Know the Difference, Save Lives

Mandatory Signs and Prohibition Signs are the silent sentinels of every Australian workplace. They’re not decoration — they’re essential tools for communication, compliance, and safety.

  • Mandatory Signs tell you what you must do to protect yourself and others.

  • Prohibition Signs tell you what you must not do to prevent harm.

The difference between a blue circle and a red slash might seem small — but on the job, it could be the difference between safety and disaster.

Next time you see a safety sign, take a moment to register the colour, the shape, and the message. Knowing the difference helps everyone get home safe — and that’s what truly matters.

 

FAQ's

  1. What is the difference between a Mandatory Sign and a Prohibition Sign? Mandatory Signs instruct what actions must be taken for safety, while Prohibition Signs indicate actions that are not allowed in specific areas.

  2. Where should Mandatory and Prohibition Signs be placed in a workplace? Mandatory Signage should be placed near the relevant action or equipment (e.g., PPE requirements), while Prohibition Signage should be placed where restricted activities or hazards are present (e.g., “No Smoking” near flammable materials).

  3. Are there legal consequences for not using the correct signage in the workplace? Yes, failing to comply with Australian standards for safety signage can lead to legal penalties and increased risk of workplace accidents.

  4. Do the colours and symbols on Mandatory and Prohibition Signs vary across Australia? No, the design standards for Mandatory and Prohibition Signage are consistent across Australia to ensure clarity and understanding in any workplace.

  5. Can I create my own safety signs for my workplace? While you can create custom signs for specific situations, they must still comply with the AS 1319-1994 standards to be legally recognised and enforceable.

For more information on Mandatory and PPE Signs see the following blogs: 

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