NYC’s Tier IV Engine Rule Is Now in Effect—Here’s What It Means for Your Business

At the beginning of 2025, the New York City Department of Environmental Protection (DEP) began enforcing new Tier IV emission standards for stationary reciprocating compression ignition internal combustion engines.

With the rule now in effect, NYC businesses that rely on stationary combustion engines for power generation, manufacturing, and industrial processes must take immediate steps to ensure compliance, or risk operational shutdowns.

What the Tier IV Rule Requires

Under this regulation, all stationary reciprocating compression ignition internal combustion engines (except emergency generators) must comply with the United States Environmental Protection Agency (EPA) Tier IV standards before receiving a renewed certificate of operation.

Here’s what that means for New York City businesses:

• Engines must meet Tier IV standards, which reduce nitrogen oxides (NOx) and particulate matter (PM) emissions by 90% compared to the previous Tier III standard.
• Non-compliant engines must be upgraded with Selective Catalytic Reduction (SCR) technology or replaced entirely.
• Unlike federal regulations that apply only to new engines, this rule applies retroactively to all stationary engines seeking a renewed certificate of operation.

How This Affects NYC Businesses

Now that the Tier IV rule is in effect, businesses must ensure their operations align with the new requirements. Facilities impacted by the change in regulation include power generation facilities, manufacturing plants, wastewater treatment plants, and industrial sites relying on stationary engines.

For companies using stationary engines, the rule presents both a compliance challenge and a financial hurdle. The sooner your Tier III stationary engines are retrofitted properly to meet the Tier IV requirements the better, as supply chain delays in hardware can be expected with the large increase in demand.

Why This Rule Matters for NYC

This regulation is a major step toward cleaner air and a healthier environment for New Yorkers. By enforcing Tier IV compliance across all applicable stationary engines, the city aims to improve air quality, support climate goals, and enhance environmental justice.

• The 90% reduction in NOx and PM emissions will significantly decrease smog, respiratory illnesses, and cardiovascular disease risks.
• NYC’s commitment to reducing greenhouse gases aligns with broader sustainability initiatives.
• Many industrial areas with high pollution levels are located in disadvantaged communities. Lower emissions mean healthier living conditions for these residents.

How Walden Can Help

If your facility is still navigating compliance with the Tier IV Engine Rule, Walden is here to assist. With the rule now fully enforced, delaying action could put your operations at a disadvantage. Contact Walden today at 516-559-6976 to develop a compliance strategy and keep your business running without disruption.