A RECD device as per CPCB norms is often presented as a straightforward answer to diesel-generator emissions, but choosing one requires careful technical and documentary evaluation. The device must be appropriate for the specific engine, supported by relevant records, installed without creating excessive exhaust restriction, and maintained throughout its working life.
RECD stands for Retrofit Emission Control Device. It is added to the exhaust system of an existing diesel generator to reduce specified pollutants before the exhaust is discharged. For businesses that continue to depend on DG sets for standby or emergency power, an appropriately selected RECD can form an important part of a wider emission-management strategy.
Why Diesel Generator Emissions Need Attention
Diesel generators are widely used where an uninterrupted electricity supply is essential. Hospitals need backup power for critical equipment, data facilities require continuity for servers and cooling, and commercial or industrial properties use DG sets during power failures. Their reliability makes them valuable, but diesel combustion also produces particulate matter and gaseous pollutants.
The quantity and composition of those emissions depend on engine design, fuel quality, maintenance, operating load, and the generator’s overall condition. An overloaded or poorly serviced engine may produce higher smoke and soot levels than a healthy engine running within its intended range.
For this reason, fitting an RECD should not replace routine engine maintenance. Injector problems, oil consumption, clogged air filters, incorrect fuel delivery, and unstable loading should be addressed before installing exhaust after-treatment equipment. Otherwise, the device may be forced to manage emissions created by a preventable mechanical fault.
How Retrofit Emission Control Technology Works
An RECD is positioned within the diesel generator’s exhaust arrangement. Depending on its design, it may use particulate filtration, catalytic treatment, or a combination of technologies. A filtration system captures soot suspended in the exhaust stream. That collected material cannot remain inside the filter indefinitely, so it must eventually be removed through regeneration or an approved cleaning process. The appropriate method depends on the RECD design and the exhaust temperatures produced during actual DG operation.
Catalytic components work differently. They encourage chemical reactions that can convert certain exhaust constituents into less harmful compounds. Their effectiveness can depend on temperature, catalyst formulation, fuel composition, and operating conditions. A manufacturer should clearly identify which pollutants its system is designed and evaluated to control. Evidence relating to particulate reduction should not be interpreted automatically as equivalent control of nitrogen oxides, hydrocarbons, or carbon monoxide.
The Importance of Generator Load
The generator’s load profile is one of the most important—and frequently overlooked—selection factors. A DG set operating regularly at a stable load can produce different exhaust temperatures from a unit started briefly for testing or used repeatedly at low load.
Temperature affects the behaviour of many filtration and catalytic systems. If exhaust conditions are unsuitable, passive regeneration may not occur as expected. Soot can then accumulate more quickly, increasing the need for cleaning or another regeneration method.
Before recommending a product, the supplier should understand how long the DG typically runs, the load it carries, and whether its use is occasional or frequent. A solution selected only from the generator’s kVA rating may fail to account for these operating realities.
What “CPCB Approved” Should Mean to a Buyer
The phrase “CPCB approved technology” is widely used in the RECD market, but it should not be accepted as a complete compliance explanation. Buyers need to identify the specific document supporting the claim. A seller should provide the applicable certificate, test report, type-approval record, or other relevant evidence for the exact model offered. That document should identify the manufacturer, product configuration, evaluated engine or power category, pollutant scope, test conditions, and any limitations contained in its annexures.
Company-level registrations and quality-management certifications can provide useful information about the organisation, but they should not be treated as substitutes for product-specific emission-performance evidence. Buyers should independently review current information published by the Central Pollution Control Board. Requirements can also vary by region. In the National Capital Region, for example, DG-set operation may be affected by directions from the Commission for Air Quality Management, including requirements that differ according to generator capacity or configuration.
Selecting an RECD for the Actual Engine
Choosing an RECD for a DG Set should begin with the engine nameplate and technical data rather than a generic capacity chart. Two generators with the same kVA rating can have different engines, exhaust-flow rates, temperature profiles, and permissible backpressure limits. The manufacturer should study the engine make, model, rated output, manufacturing year, exhaust diameter, existing silencer, stack arrangement, typical running hours, and load pattern. It should also inspect the physical space available for installation and future maintenance.
Backpressure deserves particular attention. Any equipment introduced into the exhaust line creates some degree of restriction. If the device is incorrectly sized, installed with unsuitable piping, or allowed to become heavily loaded with soot, pressure can rise beyond acceptable limits. A well-engineered system should include an appropriate method for monitoring pressure. The manufacturer must explain the normal range, the point at which maintenance is required, and the action operators should take if readings become abnormal.
Installation Is Part of Product Performance
Even a properly selected RECD can produce disappointing results if it is badly installed. The treatment unit must be supported independently, aligned correctly, sealed against exhaust leakage, and positioned where internal components can be inspected or removed. Installation may require pipe modifications, flanges, reducers, expansion connections, structural frames, insulation, temperature sensors, pressure instruments, electrical wiring, and a monitoring panel. These items should be included clearly in the technical and commercial scope.
The layout must also account for exhaust heat and vibration. Wiring should be protected from hot surfaces, while the additional weight should not be transferred incorrectly to the engine manifold or existing pipework. Once the work is complete, commissioning should document the RECD model and serial number, the DG on which it is installed, initial operating observations, and relevant pressure or temperature readings. These records create a baseline for future inspections.
Maintenance Determines Long-Term Results
An RECD is not a fit-and-forget attachment. Its service requirements depend on its technology, the condition of the engine, fuel quality, operating hours, and soot-loading rate. The supplier should provide a written maintenance schedule explaining inspection intervals, regeneration or cleaning procedures, alarm responses, and replacement requirements. Operators should record important readings and report unusual smoke, noise, leakage, or pressure behaviour.
Warranty conditions also require close attention. Buyers should establish whether coverage includes the filter, catalyst, sensors, controller, housing, piping, and installation workmanship. Any exclusions connected with engine condition, fuel quality, missed maintenance, or unauthorised modifications should be disclosed before purchase.
Regulatory Compliance Is Broader Than the Device
Installing documented emission-control technology does not automatically authorise a diesel generator to operate under every condition. DG use may remain subject to local consent conditions, emergency-use limitations, air-quality restrictions, fuel requirements, or measures implemented under the Graded Response Action Plan.
The applicable position may depend on the generator’s capacity, age, location, purpose, and technical configuration. Facility owners should verify current directions through CPCB and the relevant state pollution control board. NCR-based organisations should additionally consult CAQM’s latest notices rather than relying on an old circular or a supplier’s interpretation. A responsible RECD company will explain its product and documentation accurately, but it should not offer unsupported legal guarantees about future DG operation.
Frequently Asked Questions
What is an RECD used for?
An RECD is installed in a diesel generator’s exhaust system to reduce specified pollutants, depending on the device’s design and evaluated performance.
Is every RECD suitable for every DG set?
No. Selection depends on the engine model, exhaust flow, operating temperature, permitted backpressure, load pattern, installation space, and documented product scope.
Does CPCB issue the same requirement throughout India?
Requirements and enforcement conditions may differ by location and can be affected by central, state, NCR-specific, or local directions. Buyers should check current official sources.
Can an RECD affect generator performance?
An incorrectly selected, blocked, or poorly installed device can increase exhaust backpressure. Correct sizing, monitoring, and maintenance help protect generator operation.
How frequently should an RECD be serviced?
There is no universal interval. Service frequency depends on the technology, engine condition, running hours, operating load, soot accumulation, and manufacturer’s instructions.

Conclusion
An RECD for a DG Set can help reduce targeted diesel emissions when the equipment is correctly selected, professionally installed, and maintained according to the manufacturer’s instructions. Engine compatibility, exhaust temperature, backpressure, operating load, and filter-cleaning requirements must all be evaluated before installation. Buyers should avoid relying solely on phrases such as “CPCB approved.” Instead, they should verify the offered model’s supporting documents and check the latest CPCB, CAQM, state, and local requirements through official sources. A well-documented RECD, combined with regular engine maintenance and reliable after-sales support, offers a more responsible approach to cleaner and dependable backup power.