SCR And Marine Engine Room Ventilation

October 29, 2025

Brad Marsden

Director - Marine Air Flow International

35 Years Experience in the Marine Industry

Marine Selective Catalytic Reduction (SCR) Systems: Cleaner Solutions For Maritime Applications

The marine industry is under increasing pressure to cut harmful emissions and operate more sustainably. One of the most effective ways to achieve this is through Selective Catalytic Reduction (SCR) systems, a proven technology that reduces nitrogen oxides (NOx) in marine engines.

At Marine Air Flow International (MAFI), we work alongside shipbuilders, operators, and defence clients to ensure that our ventilation systems are designed for efficiency, compliance, long-term reliability and to work alongside SCR units.

What is a Marine SCR System?

A Selective Catalytic Reduction (SCR) system is an after-treatment solution designed to reduce NOx emissions. It works by injecting a urea-based solution, often called Diesel Exhaust Fluid (DEF) or AdBlue, into the exhaust gases. As these gases pass through a catalyst, the NOx reacts with the fluid and is broken down into nitrogen and water vapour.

This process can reduce NOx emissions by up to 90%, helping vessels meet various emission standards and supporting a cleaner marine environment.

Why Are SCR Systems Vital in Marine Operations?

Regulatory Compliance
With IMO Tier III and other regional requirements in place, SCR technology ensures vessels remain compliant in Emission Control Areas (ECAs).
Environmental Responsibility
Reduced NOx means less smog, acid rain, and air pollution—protecting both marine and coastal ecosystems.
Performance and Flexibility
SCR systems can be adapted for a wide range of marine engines, including high-performance patrol boats, commercial ferries, and defence vessels.
Future-Proofing Fleets
As emission standards continue to tighten, SCR provides a robust pathway for long-term compliance.

How SCR Systems Work

The process is straightforward yet highly effective:

Injection: Urea solution is sprayed into the exhaust stream.
Catalysis: Exhaust gases pass through a catalyst where NOx is converted.
Conversion: The reaction turns harmful NOx into nitrogen and water.
Clean Output: The result is significantly cleaner emissions leaving the stack.

How SCR Systems Can Affect Your Engine Room Temperatures

By design SCR Systems can and do run very warm. This can have a decent impact on your engine room temperatures, increasing them toward undesirable levels of heat.

If your SCR system is not encapsulated and/or insulated you can end up with a lot more heat in your engine room space. The knock on effect of this is that you can require a lot more air induction to counteract this. However if the SCR location is taken into consideration before your ventilation system is designed we can usually account for the extra heat quite effectively.

How an SCR works in a marine engine room.

MAFI’s Role in Supporting SCR Technology

At Marine Air Flow International, we understand that installing SCR systems involves more than just fitting a catalytic converter. Effective operation requires precisely engineered ventilation and airflow management. Our team provides:

Custom ventilation solutions to ensure your engine room operates at maximum efficiency, despite SCR systems.
Lightweight, durable ventilation systems, using sustainable green materials wherever possible. This helps to support your commitment to environmental considerations.
Integration expertise across a wide range of vessels, including naval ships, patrol boats, commercial ferries, and luxury yachts.
Compliance-focused designs that align with NSCV/USL codes and international maritime standards.

With over 20 years of experience in marine ventilation, MAFI has become a trusted partner for operators seeking safe, reliable, and regulation-ready systems.

The Future of Marine Emissions Control

As shipping transitions toward alternative fuels such as LNG, methanol, and hybrid propulsion, after-treatment solutions like SCR will continue to play a critical role. MAFI is committed to supporting this transition by delivering future-focused ventilation systems that complement the latest emission control technologies.

Final Thoughts

Marine Selective Catalytic Reduction systems are essential for meeting today’s strict emission standards and building a sustainable future for shipping. With the right design, integration, and ventilation support, SCR technology not only keeps vessels compliant but also demonstrates a strong commitment to environmental responsibility.

At Marine Air Flow International, we help shipbuilders and operators get the most from their SCR installations, delivering systems that are efficient, reliable, and built for the future of marine engineering.

Keep your engine room cool even with an SCR unit.

< Older Post

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56 Meter RORO Ferries Project For Abu Dhabi

By Brad Marsden • June 10, 2025

Optimising Engine Room Ventilation for Abu Dhabi’s High-Speed Ro-Pax Ferries As part of Abu Dhabi’s ongoing investment in advanced maritime infrastructure, the AD Ports Group commissioned two high-speed Ro-Ro ferries to operate between the UAE mainland and Delma Island. Carrying 250 passengers and 25 cars per trip at a service speed of over 30 Knots is pretty impressive , and you'd have to agree they are certainly very tidy looking Roll On Roll Off Ferries!! Designed for both passenger comfort and operational performance, these cutting-edge vessels required a ventilation solution that could meet the rigorous demands of the Gulf’s climate and the intense operating conditions of four powerful MTU engines per vessel. Our team was proud to be selected to design and deliver the engine room ventilation system for these state-of-the-art ferries, ensuring they remain safe, efficient, and reliable at sea. Engineering the Future of Fast Ferry Travel Built to carry up to 194 passengers and 25 vehicles, each of the 56-metre-long catamarans has been equipped with four MTU 16V4000M65L high-performance engines driving Kongsberg KaMeWa waterjets. This powerful propulsion setup enables cruising speeds of up to 35 knots, making the ferries among the fastest in their class within the region. Inside, the vessels feature modern amenities such as a VIP lounge, children’s play area, two cafes, five toilets, and full wheelchair accessibility, highlighting AD Ports Group’s commitment to both efficiency and passenger experience. Operating in the heat of the Persian Gulf, however, presents unique engineering challenges. The heart of this lies within the engine room where temperatures, airflow, and safety systems must be tightly controlled to prevent overheating, ensure compliance, and protect both crew and machinery. A Tailored Ventilation Solution for Demanding Conditions The brief for this project was clear: create a ventilation system that could not only manage the extreme thermal loads generated by four high-output marine engines but also comply with international marine safety standards, including fire isolation and redundancy protocols. Key features of the system we delivered include: Marine-Grade Ventilation Dampers : Built from corrosion-resistant stainless steel, our dampers are designed for longevity and reliability in a saltwater environment. Integrated Auto Close Capability : The dampers are configured to close rapidly in the event of a fire, helping to isolate the engine room and restrict oxygen supply. High Airflow Capacity : Designed specifically for the compact, high-output layout of the engine rooms, the system allows for maximum airflow and heat dissipation under full load. Moisture and Salt Mist Defence: Our Intake grilles are known globally for their excellent capability of reducing salt mist and spray into your engine room. Here they allow a vessel operating in already extreme conditions to require far less ongoing equipment replacement. Redundancy & Safety : With automated control options and manual overrides, the system ensures continuous operation and safety during engine shutdowns or emergencies. Delivering Results at Sea With the ventilation system now fully installed and operational, the Ro-Pax ferries have successfully completed sea trials and are ready to begin service. The performance of the engine room ventilation under load has exceeded expectations, maintaining optimal operating temperatures even during high-speed runs in the peak Gulf heat. In addition to thermal performance, the system’s fire isolation capability offers an added layer of safety, helping these ferries meet stringent international compliance standards while delivering peace of mind for operators and passengers alike. Reflecting on the Project This project underscores the critical importance of high-performance ventilation systems in modern vessel design. From the intense thermal loads of multi-engine configurations to the need for rapid fire response and corrosion resistance, every detail matters when it comes to marine safety and reliability. We’re proud to have played a key role in supporting this milestone for AD Ports Group and Abu Dhabi’s maritime future and we look forward to bringing this level of engineering excellence to future vessel builds across the region and beyond. Talk to Us About Your Marine Ventilation Needs Whether you’re designing a new-build high-speed ferry or retrofitting an existing vessel, we offer tailored ventilation solutions that combine safety, efficiency, and performance. Get in touch with our team today to learn how we can support your next marine engineering project.