A DG set pollution control RECD system is a retrofit emission-control solution designed to help reduce particulate emissions from eligible in-use diesel generator engines. For businesses that depend on DG sets for backup or continuous power, understanding how RECD technology works is important before selecting, installing, or maintaining a system.

CPCB has published a specific system and procedure for emission-compliance testing of Retrofit Emission Control Devices (RECDs) for diesel power-generating set engines up to 800 kW gross mechanical power. The procedure was revised on July 24, 2023. However, an RECD should not be viewed as a universal product that can be fitted to every generator without evaluation. Engine specifications, applicable requirements, product certification, installation conditions, and operating characteristics all need to be considered.

What Does RECD Mean?

RECD stands for Retrofit Emission Control Device.

The word “retrofit” is important. An RECD is intended for an existing diesel engine rather than being part of the engine's original manufacturing configuration.

This makes retrofit technology useful when an organization already operates diesel generators and needs to address applicable emission-control requirements without replacing the entire generator.

An RECD can form part of a broader pollution-control strategy for eligible DG sets, but its suitability depends on the particular engine and the certified application of the device.

Why Are RECD Systems Used With DG Sets?

Diesel generator engines release exhaust emissions when operating. Depending on the engine, fuel, operating condition, maintenance condition, and other factors, these emissions can include particulate matter and gaseous pollutants.

An emission-control device can help address particulate emissions from an eligible generator.

This is particularly relevant for facilities such as:

• Manufacturing plants

• Hospitals

• Commercial complexes

• Data centres

• Hotels

• Educational institutions

• Telecom sites

• Construction facilities

• Industrial units

• Large residential developments

For these facilities, the generator may be required only during power interruptions or may operate more frequently depending on the application.

An appropriately selected retrofit system can therefore become an important component of the facility's environmental-management planning.

How Does an RECD System Work?

The exact operating principle depends on the RECD technology and product design.

At a broad level, the device is integrated into the generator's exhaust system so that particulate matter in the exhaust can be captured or otherwise controlled before the exhaust is released.

Some systems can also include monitoring and control components that help the system operate within its intended parameters.

The important point is that an RECD is not simply an ordinary silencer.

A silencer primarily addresses exhaust noise, whereas an emission-control device is designed for emission reduction.

The two components can have different purposes even though they may both be installed within the exhaust arrangement.

RECD Is More Than an Exhaust Component

When evaluating an RECD, buyers should consider the complete installation rather than looking only at the main housing.

Depending on the technology, an installation can involve:

• RECD unit

• Sensors

• Controller

• Exhaust connections

• Mounting arrangements

• Electrical connections

• Monitoring functions

• Alarm or diagnostic functions

The exact configuration varies according to the product.

Therefore, the quotation should clearly identify what is included.

A product that appears cheaper may have installation, controller, sensors, exhaust modification, commissioning, or maintenance services excluded.

Understanding CPCB's RECD Framework

CPCB's published RECD 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. It includes provisions related to applicability, certification, testing equipment, test procedures, and technical requirements.

This framework is particularly important when evaluating claims about an RECD being “CPCB approved.”

A buyer should ask:

• Which exact product has been evaluated?

• Which engine range does it cover?

• What power range applies?

• What certification information is available?

• Which certification agency is identified?

• Does the proposed application match the documented range?

These questions are more useful than relying on a general marketing statement.

Is Every RECD Suitable for Every DG Set?

No.

CPCB's published manufacturer information demonstrates that certified RECD products can have different applicability ranges.

For example, the CPCB list dated May 9, 2025 identifies certified RECD manufacturers and shows different engine-power ranges, Phase I/Phase II applicability, and certification agencies.

Consequently, a facility should not choose an RECD merely because the manufacturer appears on a published list.

The exact product and its applicability should be verified against the specific generator engine.

Start With Your Engine Specifications

Before asking for an RECD quotation, collect the generator's technical details.

At minimum, record:

• Engine manufacturer

• Engine model

• Engine serial number

• Gross mechanical power

• Rated speed

• Generator rating

• Emission category or phase, where applicable

• Existing exhaust configuration

Gross mechanical power is particularly important because the CPCB RECD procedure identifies an applicability scope up to 800 kW gross mechanical power.

Do not depend exclusively on the DG set's kVA rating when discussing RECD selection.

Why Engine Matching Matters

Imagine a facility operating several DG sets.

One may have a relatively small engine, while another may have a significantly larger engine. Even if both generators perform the same basic function, their engines can have different specifications and exhaust characteristics.

An RECD certified for one application should not automatically be assumed to be appropriate for another.

Engine matching helps establish whether:

• The product is within its certified range

• The power range is appropriate

• The relevant phase is covered

• Installation requirements can be satisfied

• The proposed system is technically suitable

The Role of Sensors and Controllers

Modern emission-control systems can include electronic monitoring components.

Depending on the product, sensors and controllers may monitor operating conditions and provide information to the operator.

A controller may support functions such as:

• System status monitoring

• Fault indication

• Alarm generation

• Sensor monitoring

• Operational diagnostics

The precise features vary between technologies.

Therefore, buyers should request the product's technical datasheet rather than assuming that every RECD provides identical monitoring capabilities.

Installation Requires Technical Planning

Installing an RECD into an existing exhaust system should begin with a site assessment.

The technical team should inspect:

Exhaust Layout

• Existing pipe diameter

• Exhaust routing

• Silencer arrangement

• Available installation space

Mechanical Requirements

• Equipment weight

• Mounting structure

• Support requirements

• Maintenance access

Electrical Requirements

• Controller location

• Power supply

• Sensor wiring

• Cable routing

Engine Considerations

• Existing exhaust configuration

• Operating conditions

• Back-pressure considerations

CPCB's testing framework includes evaluation of exhaust back pressure, making this an important engineering consideration during retrofit planning.

What Are the Benefits of an RECD System?

1. Retrofit Capability

One of the main advantages is that the system can be applied to an existing eligible diesel engine rather than requiring complete generator replacement.

2. Particulate Emission Control

RECD technology is primarily associated with particulate-matter reduction in the applicable testing and certification framework.

The actual performance should be evaluated using the relevant certified product documentation.

3. Supports Environmental Management

An appropriately selected emission-control system can form part of an organization's broader environmental-management program.

4. Potentially Lower Than Generator Replacement

For an existing generator that remains operationally useful, a retrofit approach may be considered instead of replacing the entire power-generation system.

The economic decision should be based on the specific generator, installation cost, expected operating life, maintenance requirements, and regulatory situation.

5. Existing Generator Can Continue Serving Its Purpose

A properly planned retrofit can allow an existing generator to remain part of the facility's backup-power strategy while emission-control measures are addressed.

How to Identify a Properly Documented RECD

When searching for an RECD device as per CPCB norms, avoid selecting a product based solely on a supplier's website description.

Request:

• Manufacturer name

• Exact RECD model

• Product/part number

• Applicable engine range

• Applicable power range

• Phase applicability

• Certification details

• Test documentation

• Installation requirements

CPCB's published manufacturer list provides specific applicability information and identifies certification agencies for listed products.

This makes documentation an important part of the buying process.

Maintenance After Installation

An RECD is not a “fit-and-forget” component.

Maintenance requirements depend on the technology, but the facility should establish a schedule covering:

• Visual inspection

• Sensor inspection

• Controller checks

• System diagnostics

• Cleaning where specified

• Component replacement where required

• Exhaust inspection

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

Poor engine maintenance can also affect exhaust conditions and the overall operation of an emission-control system.

What Happens If the RECD Is Poorly Selected?

Choosing an unsuitable product can create technical and operational problems.

Potential issues include:

• Incorrect fitment

• Excessive exhaust restriction

• Inadequate emission-control performance

• Frequent alarms

• Maintenance difficulties

• Installation complications

• Documentation gaps

This is why the cheapest quotation is not necessarily the best solution.

The correct question is:

Is this product properly matched, documented, installed, and supported for my DG set?

A Practical Selection Process

Facility owners can simplify RECD selection by following a structured approach.

Step 1: Identify the DG Set

Record engine model and gross mechanical power.

Step 2: Review Applicable Requirements

Check current CPCB information and relevant state/local requirements.

Step 3: Shortlist Suitable Manufacturers

Use reliable certification and product information.

Step 4: Verify the Exact Product

Confirm model, application range, and supporting documents.

Step 5: Conduct a Site Survey

Assess exhaust, mounting, electrical, and maintenance requirements.

Step 6: Compare Complete Quotations

Include equipment, installation, commissioning, warranty, and maintenance.

Step 7: Commission the System

Ensure installation and commissioning are documented.

Step 8: Maintain Records

Keep certification, installation, maintenance, and service documents together.

Common Questions

Can an RECD be installed on an existing generator?

The purpose of an RECD is to provide a retrofit emission-control solution for eligible in-use diesel engines. Suitability must be established for the particular engine and product.

Does an RECD replace the generator's silencer?

Not necessarily. Their functions are different, and the final exhaust configuration depends on the generator and selected system.

Does CPCB certify every RECD product available in the market?

Buyers should verify the exact product and manufacturer against current official CPCB information rather than assuming that every commercially available device has the same certification status. CPCB publishes a list of certified RECD manufacturers with applicability details.

Is an RECD suitable for generators above 800 kW?

The cited CPCB RECD procedure covers diesel power-generating set engines up to 800 kW gross mechanical power. Applications outside that scope should be assessed against the applicable current regulatory and technical requirements rather than assumed to be covered.

How often should an RECD be serviced?

The maintenance interval depends on the technology and manufacturer's instructions. Obtain a written maintenance schedule with the product documentation.

Final Thoughts

A DG set pollution-control strategy should begin with understanding the generator itself. An RECD is a retrofit emission-control technology intended for eligible in-use diesel generator engines, and CPCB has established a technical framework for evaluating such devices. The published framework and manufacturer information show why product selection needs to consider engine power, application range, certification details, and technical compatibility rather than relying on generic claims. For businesses considering an RECD, the most reliable approach is to identify the engine, verify the applicable requirements, check the exact product documentation, conduct a site assessment, and plan installation and maintenance properly.