When Flame Projection Test Isn’t Enough: Understanding the UN TDG Enclosed Space Ignition Test for Aerosol Classification 

If your company manufactures, imports, or distributes aerosol products in Canada or internationally, it’s critical to understand the full scope of classification requirements under the United Nations Recommendations on the Transport of Dangerous Goods (UN TDG). One of the most misunderstood areas of aerosol classification is the assumption that a product showing no flame projection in the ignition distance test is automatically a non-flammable aerosol.  

This is not true.  

Even if your aerosol product doesn’t project a flame during the ignition distance test, you still need to conduct the enclosed space ignition test to determine whether it can be considered non-flammable under the UN TDG system. Failing to complete both required tests could lead to misclassification—resulting in non-compliance, enforcement action, transport issues, or worse, safety risks for users and handlers.  

In this blog, we’ll walk through:  

• The UN TDG criteria for aerosol classification 

• The two required flammability tests: Ignition Distance and Enclosed Space Ignition 

• Why passing one test isn’t enough 

• How Dell Tech can help with compliant aerosol testing and classification  

The Regulatory Context: Aerosol Classification Under UN TDG 

The United Nations Recommendations on the Transport of Dangerous Goods-commonly referred to as the UN TDG Purple Book- lays out the framework used by countries around the world, including Canada, to classify and label dangerous goods during transport. For aerosols, the applicable classification is Class 2, Division 2.1 (Flammable Gases) if the aerosol meets flammability criteria. If it doesn’t, it may be considered non-flammable and not regulated under this class for transport purposes.  

But how is flammability determined?  

Under the UN TDG system, there are two standardized tests that must be conducted to assess the flammability of an aerosol:  

1. Ignition Distance Test (Flame Projection Test) 
2. Enclosed Space Ignition Test  

It is the combined results of these two tests that determine whether an aerosol is flammable or non-flammable under UN TDG.  

Ignition Distance Test: The First Step 

The ignition distance test assesses whether the contents of an aerosol can project a flame when discharged in the direction of a small ignition source. The test procedure involves: 

• Spraying the aerosol toward a flame (at 15 cm, 30 cm, and 45 cm distances) 
• Observing whether a flame is projected 
• Measuring the length of flame projection, if present  

If your product does project a flame, it may be considered flammable and subject to Class 2.1 classification. If your product does not project a flame, it may seem intuitive to assume it’s non-flammable—but this is where many companies go wrong. Passing the ignition distance test does not exempt you from additional testing. 

The Enclosed Space Ignition Test: The Missing Link 

The enclosed space ignition test simulates conditions where flammable vapors could build up in a confined area- like inside a shipping container, delivery truck, or storage room. The purpose is to determine whether the aerosol’s vapors alone, without visible flame projection, are capable of igniting an explosive atmosphere. 

How the Test Works: 

• The aerosol is discharged into a standard enclosed chamber for a specified duration (typically 4 seconds). 
• The chamber contains a spark ignition source. 
• Observers check whether ignition occurs inside the chamber.  

If ignition occurs, the aerosol cannot be considered non-flammable—even if the ignition distance test showed no flame projection.  

If no ignition occurs during the enclosed space test and there was no flame projection, only then can the aerosol be classified as non-flammable under UN TDG.  

A product with no flame projection is not necessarily non-flammable. The absence of flame must be confirmed by a negative result in the enclosed space ignition test to support a non-flammable claim.  

Real-World Consequences of Misclassification  

1. Regulatory Non-Compliance

If a company declares an aerosol product as non-flammable based solely on the ignition distance test, it may be non-compliant with Canadian Transportation of Dangerous Goods (TDG) regulations, which are harmonized with UN TDG. Such misclassification could lead to: 

• Product recalls 
• Fines or penalties 
• Transport delays at border crossings 
• Reputational damage 

2. Improper Shipping and Packaging

Flammable aerosols require: 

• Specific packaging requirements 
• Flammable gas hazard labels 
• Declared shipping descriptions under Class 2.1  

Incorrect classification means your product may be packed and shipped without appropriate hazard controls—potentially endangering warehouse workers, transport personnel, or consumers.  

3. Invalid Safety Data Sheets (SDS)

If your SDS lists the product as non-flammable, but testing was incomplete or inaccurate, your document is technically invalid under GHS and WHMIS requirements. 

Industry Misunderstandings: Common Myths Debunked 

Case Study Example: Cleaning Product Aerosol 

Imagine your company launches a new cleaning spray aerosol. You test it using the ignition distance method. No flame projection is observed at any distance, so you label it as “non-flammable” on the SDS and ship it without TDG markings. But then, during a regulatory inspection or audit, you’re asked to provide the enclosed space ignition test results. You didn’t perform the test—because you assumed it wasn’t necessary. Your product is now at risk of being reclassified as flammable. You may face regulatory citations, and your shipments could be held at customs. This is why Dell Tech always advises clients to conduct both tests when classifying aerosols for transport. 

Dell Tech’s Aerosol Testing Services 

At Dell Tech, we offer comprehensive UN TDG aerosol testing services, including: 

• 🔥 Ignition Distance Testing 
• 🔥 Enclosed Space Ignition Testing 
• 📦 Aerosol Classification Reports for Transport Compliance 
• 📄 SDS Authoring and TDG Packaging Recommendations  

We have over 40 years of experience in chemical and regulatory compliance, and our in-house lab is equipped to handle full aerosol flammability evaluation to help you meet your obligations with confidence. Our team can help you:  

• Determine whether your product is flammable under UN TDG 
• Avoid costly misclassification mistakes 
• Ensure accurate SDS hazard communication 
• Provide data for WHMIS and GHS classification globally 

📎 Contact Dell Tech for UN TDG aerosol testing 

Final Thoughts: Do It Right-Do Both Tests 

In summary, if your product is an aerosol and you want to claim it’s non-flammable, you must go beyond the ignition distance test. The enclosed space ignition test is a critical-and required-step to verify your claim. Failure to do so may result in misclassification, which can lead to: 

• Transport violations 
• Invalid hazard communication 
• Legal liability 
• Safety risks to workers and users 

Don’t let assumptions put your business at risk. Dell Tech offers the complete suite of UN TDG flammability tests you need to support a compliant, defensible classification. 

📞 Ready to confirm your aerosol’s classification? 

Book your UN TDG flammability testing today 
📧 info@delltech.com | ☎️ 519-858-5021 
📎 Learn more about our laboratory services 

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