Choosing an RECD device as per CPCB normsrequires more than selecting an emission-control product from a supplier's catalogue. Generator owners need to understand the applicable technical requirements, identify the correct RECD for the engine, verify supporting documentation, and ensure that installation and maintenance are properly planned.

Retrofit Emission Control Devices (RECDs) are designed for eligible in-use diesel generator applications. The Central Pollution Control Board (CPCB) has published a specific system and procedure for emission-compliance testing of RECDs for diesel power-generating set engines up to 800 kW gross mechanical power. The procedure was revised on July 24, 2023. For businesses, commercial facilities, institutions, and industrial sites operating diesel generators, understanding this framework can make RECD procurement more systematic and reduce the risk of selecting an unsuitable product.

What Is a RECD?

RECD stands for Retrofit Emission Control Device.

Unlike an emission-control system designed as part of a new engine, an RECD is intended to be installed on an existing, in-use diesel generator engine. Its purpose is to control specified exhaust emissions through a retrofit solution.

The technology and configuration can vary depending on the product and application. Therefore, an RECD should not be treated as a universal component that can simply be attached to every diesel generator.

The engine's characteristics, power range, applicable phase, exhaust arrangement, and product documentation all matter when selecting a suitable device.

What Does “as per CPCB Norms” Mean?

The phrase “as per CPCB norms” is widely used when searching for RECD products, but it should be interpreted carefully.

CPCB has established a formal system and procedure for emission-compliance testing of RECDs for diesel genset engines up to 800 kW gross mechanical power. The procedure covers matters such as applicability, emission requirements, certification, test equipment, test conditions, and testing procedures.

Therefore, a buyer should not consider a product compliant merely because its advertisement says “CPCB approved.”

Instead, the exact product should be verified against the relevant documentation and applicable requirements.

Which DG Sets Are Covered?

CPCB's published RECD procedure is specifically for diesel power-generating set engines up to 800 kW gross mechanical power.

This is an important distinction because generator ratings are often discussed in kVA, while the CPCB RECD framework refers to gross mechanical power in kW.

A buyer should therefore obtain the engine's actual technical information instead of trying to select an RECD solely from the generator's electrical rating.

For example, knowing that a generator is rated at a particular kVA level may not be enough. The supplier may also need the:

• Engine manufacturer

• Engine model

• Engine serial number

• Gross mechanical power

• Rated speed

• Engine phase

• Existing exhaust details

This information helps establish whether the proposed RECD is appropriate for the specific application.

Why Engine Identification Is Important

Two diesel generators with similar electrical ratings can have different engine configurations.

They may differ in:

• Engine manufacturer

• Engine model

• Gross mechanical power

• Emission phase

• Exhaust flow

• Exhaust temperature

• Existing exhaust arrangement

Consequently, an RECD suitable for one generator should not automatically be assumed to be suitable for another.

The correct approach is to match the device to the documented engine application.

Understand Phase Applicability

Another important part of RECD selection is determining whether the product is applicable to the relevant engine phase.

CPCB's published list of certified RECD manufacturers dated May 9, 2025 identifies products according to specified engine-power ranges and indicates whether their applicability is for Phase I, Phase II, or both.

This means buyers should not simply select an RECD based on manufacturer name.

Instead, verify:

Engine phase → Applicable power range → RECD model → Supporting certification information

The exact applicability should be confirmed from current official documentation before purchase.

CPCB Certification and Testing Framework

CPCB's RECD procedure provides a structured framework for emission-compliance testing.

The published procedure includes requirements relating to:

• Base engine identification

• RECD identification

• Test conditions

• Emission measurement

• Performance evaluation

• Certification

• Applicable engine types

• Product identification

This framework is important because it creates a technical basis for evaluating retrofit devices rather than relying solely on supplier marketing claims.

For a buyer, the practical lesson is simple:

Ask for product-specific documentation.

A generic brochure is useful for understanding a product, but it should not replace relevant certification or test documentation.

What Should You Verify Before Selecting an RECD?

A practical verification process can begin with the generator.

Step 1: Record Engine Details

Collect the engine nameplate and technical information.

Step 2: Confirm Gross Mechanical Power

Do not estimate this from the generator's kVA rating.

Step 3: Determine Applicable Phase

Confirm the relevant engine phase.

Step 4: Identify the RECD Model

Obtain the exact model and part number.

Step 5: Check the Documented Application

Verify that the proposed product covers the engine and power range.

Step 6: Review Supporting Documents

Request relevant certification/test information.

Step 7: Assess Installation

Review the exhaust arrangement, available space, mounting and other site requirements.

Step 8: Confirm Service

Understand warranty, maintenance and spare-parts support.

This process helps turn RECD selection into a documented technical decision.

Do Not Select an RECD Solely by Generator kVA

This deserves particular attention.

A generator may be described commercially as:

• 100 kVA

• 250 kVA

• 500 kVA

• 750 kVA

However, the RECD technical framework uses gross mechanical power of the engine.

The generator's electrical rating and engine's mechanical power are related, but they are not interchangeable specifications.

Therefore, obtain the engine documentation before asking a supplier to recommend a specific device.

Check the Exhaust System Before Installation

Selecting the product is only one part of the project.

The existing exhaust arrangement should also be assessed.

Important details include:

• Exhaust pipe diameter

• Existing silencer

• Pipe routing

• Number of bends

• Available connection points

• Mounting arrangement

• Available installation space

• Maintenance access

An RECD retrofit can require mechanical modifications depending on the existing configuration.

A site survey can therefore be valuable before finalizing the installation scope.

Exhaust Back Pressure Matters

Any retrofit connected to the exhaust system should be assessed with regard to exhaust back pressure.

CPCB's RECD testing procedure includes exhaust back pressure as one of the technical parameters considered during testing.

The final installation should also take into account the engine manufacturer's applicable requirements.

Before installation, ask the supplier or technical team:

What is the expected back pressure with the proposed RECD installed?

The answer should be supported by appropriate engineering information.

Certification Does Not Mean “One Product Fits All”

CPCB's published manufacturer list shows that certified RECD products have different applicability ranges.

The May 9, 2025 list identifies manufacturers and their specified ranges for in-use diesel genset engines, along with Phase I/Phase II applicability and certification agency information.

This demonstrates why product selection should be application-specific.

A buyer should verify the exact:

• Manufacturer

• RECD model

• Engine range

• Power range

• Phase

• Certification agency

• Supporting documentation

before placing an order.

How to Evaluate RECD Documentation

A strong documentation package should make it possible to identify the product clearly.

Look for information such as:

Product Information

• Manufacturer

• Product name

• Model

• Part number

Application Information

• Engine type

• Engine power range

• Phase

• Applicable DG-set range

Testing/Certification Information

• Relevant test or certification reference

• Certification agency

• Applicable test procedure

• Supporting technical documents

The exact documents required can vary by product and application.

If a supplier provides only a generic statement such as “CPCB approved,” request additional product-specific evidence.

What About New and Existing DG Sets?

It is important to distinguish between requirements for new genset engines and the retrofit framework for in-use engines.

CPCB separately publishes procedures concerning compliance with emission standards for new power-generating-set engines up to 800 kW.

The RECD procedure, by contrast, addresses retrofit emission-control devices for eligible in-use diesel genset engines.

Therefore, buyers should first determine whether they are dealing with:

• A new generator purchase

• An existing generator requiring a retrofit

• Replacement of an existing emission-control system

• Modification of an existing installation

The applicable regulatory pathway may differ.

Installation Is Part of the Compliance Picture

Even when a suitable product has been selected, installation should be handled carefully.

The project may involve:

• Mechanical mounting

• Exhaust connection

• Pipe fabrication

• Sensor installation

• Controller installation

• Electrical connections

• System checks

• Commissioning

The exact scope depends on the RECD technology and site configuration.

The purchase order should clearly define who is responsible for each part of the work.

Do You Need a Controller?

Some RECD solutions can include electronic control and monitoring components.

Depending on the specific product, a system may incorporate:

• Controller

• Sensors

• Display or interface

• Alarm functions

• Diagnostic information

Do not assume these components are automatically included.

Ask the supplier to clearly state:

What is included in the quoted RECD package?

This prevents confusion over additional equipment and installation costs.

Maintenance After Installation

Installing an RECD does not eliminate the need for ongoing maintenance.

The manufacturer should provide suitable maintenance instructions for the specific product.

Depending on the technology, maintenance can involve:

• Visual inspection

• Cleaning

• Sensor checks

• Controller diagnostics

• Exhaust inspection

• Replacement of components

• Periodic servicing

Generator maintenance should also continue according to the engine manufacturer's recommendations.

An emission-control retrofit should work alongside proper engine maintenance, not replace it.

What Is a DG Generator Emission Control Device?

The term DG generator emission control device can refer broadly to equipment designed to control emissions from diesel generator exhaust.

An RECD is a specific type of retrofit emission-control solution intended for eligible in-use diesel genset applications.

For buyers, the distinction is useful because not every exhaust-treatment product marketed for a generator necessarily falls within the same certification or testing framework.

Therefore, ask the supplier to identify the exact technology, product model and supporting documentation rather than relying only on a generic description.

How CPCB's Published Manufacturer List Can Help Buyers

CPCB publishes information on manufacturers certified for RECDs applicable to diesel genset engines up to 800 kW for specified capacity ranges.

The published May 9, 2025 list includes:

• Manufacturer name

• Applicable engine-power range

• Phase I/Phase II applicability

• Certification agency

For example, the list shows that different manufacturers have different certified power ranges rather than one universal range for all products.

This makes the list useful as a starting point for verification.

However, buyers should still check the current official information and confirm the exact product being offered.

Common Compliance Mistakes

Generator owners can avoid several common problems by not making assumptions.

Mistake 1: Selecting by kVA Alone

Obtain the engine's gross mechanical power.

Mistake 2: Trusting Generic “CPCB Approved” Claims

Request product-specific documentation.

Mistake 3: Ignoring Engine Phase

Confirm whether the product applies to the relevant phase.

Mistake 4: Skipping the Site Survey

Assess the exhaust arrangement and available space.

Mistake 5: Ignoring Back Pressure

Review technical requirements before installation.

Mistake 6: Assuming Certification Equals Site Compliance

Site-specific requirements should be verified separately.

Mistake 7: Ignoring Maintenance

Follow the manufacturer's maintenance recommendations.

How to Maintain a Strong RECD Compliance File

A facility should consider maintaining a dedicated record for each DG set.

The file can contain:

Generator Information

• Engine model

• Serial number

• Gross mechanical power

• Generator rating

RECD Information

• Manufacturer

• Model

• Part number

• Technical datasheet

Certification

• Test/certification documents

• Certification agency

• Applicability information

Installation

• Site survey

• Installation details

• Commissioning report

Maintenance

• Service reports

• Inspection records

• Component replacement records

Regulatory

• Relevant CPCB documents

• Applicable State Pollution Control Board/PCC requirements

• Site-specific consent conditions, where applicable

Maintaining these records can make future verification and servicing easier.

How to Choose a Suitable RECD Supplier

A supplier should be evaluated on more than product availability.

Consider whether the supplier can provide:

• Technical consultation

• Product documentation

• Application assessment

• Site survey

• Installation

• Commissioning

• Warranty

• Spare parts

• After-sales service

A supplier that asks detailed questions about the generator before recommending a product is generally taking a more application-focused approach.

Why Current Official Verification Matters in 2026

Environmental compliance information should not be treated as permanently fixed.

CPCB's website continues to publish updated announcements, technical information, directions, rules and other regulatory material. Its current website also advises users about official CPCB communications and activities.

Therefore, an old article, quotation, certificate or social-media post should not automatically be treated as the latest regulatory position.

Before purchasing an RECD, verify the current applicable requirements through official CPCB information and, where relevant, the applicable State Pollution Control Board or Pollution Control Committee.

Frequently Asked Questions

Is an RECD required for every diesel generator in India?

Requirements depend on the applicable regulations, generator characteristics, installation and site-specific conditions. Do not assume that every DG set has exactly the same requirement. Verify the current rules and requirements applicable to the specific installation.

What does CPCB's RECD procedure cover?

CPCB's published procedure provides a framework for emission-compliance testing of retrofit emission-control devices for diesel power-generating set engines up to 800 kW gross mechanical power.

Can I select an RECD based only on generator kVA?

It is better to obtain engine-specific information, particularly gross mechanical power and engine model, before selecting the product.

How do I verify a supplier's CPCB-related claim?

Ask for the exact RECD model, applicable engine range, phase applicability, certification/test information and certification agency. Then compare those details with current official CPCB information.

Does installing an RECD automatically make a DG set compliant?

Not necessarily. Product documentation, technical suitability, installation, maintenance and the requirements applicable to the specific site all need to be considered.

Does CPCB publish RECD manufacturer information?

Yes. CPCB publishes a list of manufacturers certified for RECDs for specified ranges of in-use diesel genset engines, including applicability and certification-agency information.

Conclusion

Selecting an RECD device as per CPCB norms should be approached as a technical and regulatory verification exercise rather than a simple equipment purchase. The starting point is the generator itself. Identify the engine, confirm its gross mechanical power, determine the relevant phase, and understand the existing exhaust arrangement. Then select an RECD whose documented application matches the generator. For organizations looking for a DG generator emission control device, the important question is not simply whether a product is advertised as “CPCB approved.” The stronger approach is to verify the exact product, its applicable engine and power range, supporting certification or test documentation, installation requirements, and current regulatory applicability.