“Tier 3”, “Tier 4 Final” and “Stage V” describe emissions standards that apply according to the market, engine category and application. They address nitrogen oxides (NOx) and fine particulate matter, among other emissions. When choosing a generator, check the certification of the exact engine, not just the generator set's commercial label.
What is the difference between Tier 3, Tier 4 Final and Stage V?
| Standard | Reference | Key points |
|---|---|---|
| Tier 3 | United States and related North American standards, depending on the category | An earlier stage than Tier 4, with less stringent emissions limits. Exhaust treatment depends on the engine. |
| Tier 4 Final | EPA, nonroad diesel engines in the United States | Stricter limits for NOx and particulate matter. Depending on the engine, equipment may include an SCR catalyst with DEF, a diesel particulate filter (DPF) or other combinations. |
| Stage V | European Union, nonroad mobile machinery | A separate European framework that includes particle number requirements for covered categories. Technical solutions vary with engine power and model. |
You may hear “Tier 5 Final”, but that is not the name of these standards. It usually reflects confusion between Tier 4 Final (EPA) and Stage V (European Union). The two systems are not automatically interchangeable: the engine specification sheet must state the applicable certification.
What is urea (DEF or AdBlue) used for?
Diesel exhaust fluid, called DEF or AdBlue, contains 32.5% urea and 67.5% deionized water. In an engine equipped with SCR, it is injected into the exhaust to help the catalyst reduce NOx. It is stored in a separate tank: never pour it into the diesel tank. An engine without SCR does not necessarily use DEF, even if it meets a recent standard.
What about the particulate filter?
The DPF traps soot and particulate matter; SCR mainly treats NOx with the help of DEF. Some engines combine DPF, SCR and a diesel oxidation catalyst (DOC), while others use a different configuration. When a DPF is fitted, follow the manufacturer's regeneration and maintenance instructions.
What should you check for a generator in Quebec?
In Canada, requirements may differ depending on whether the engine is intended for a stationary standby set or a mobile unit, as well as its manufacturing date and category. Before buying, ask for the exact engine designation, emissions certification, presence of SCR or a DPF, DEF requirements and operating conditions. Have the supplier of the specific model confirm which requirements apply to your installation.
To prepare your project, browse the Perkins power ratings shown and request the specification sheet for the proposed set.
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