can an RECD for DG Set actually reduce diesel exhaust odour?Diesel generator exhaust has a distinctive smell that can become noticeable around industrial facilities, commercial buildings, construction sites, and temporary power installations. This often leads to a practical question:

The answer is yes, but with an important qualification. An RECD can reduce some of the compounds responsible for diesel exhaust smell, particularly when it incorporates an oxidation catalyst and operates at an appropriate exhaust temperature. However, it cannot eliminate every possible source of odour.

Understanding the source of the smell is therefore important before expecting an emission-control device to solve the problem.

What Causes Diesel Exhaust Odour?

“Diesel smell” can describe several different odours. Some come directly from incomplete combustion, while others may originate from fuel, lubricating oil, leaks, or the surrounding installation.

Unburned and partially burned fuel compounds are important contributors to diesel exhaust odour. During combustion, not all fuel is converted completely, particularly during cold starts, low-load operation, or certain transient conditions.

CPCB's RECD procedureThe focuses primarily on controlling particulate emissions from in-use diesel engines and establishes requirements for testing and certification of retrofit emission-control devices. The odour question is therefore related to the chemistry of the device rather than being the primary basis for RECD certification.

How Can an RECD Affect Odour?

Many RECD configurations combine particulate filtration with an oxidation catalyst. The particulate section captures soot, while the catalyst can promote oxidation of certain gaseous pollutants such as hydrocarbons and carbon monoxide.

This distinction matters because some compounds contributing to the oily or sharp character of diesel exhaust are hydrocarbons and partial-combustion products.

A warm oxidation catalyst can therefore reduce some of these compounds before the exhaust leaves the stack. Aceget's technical explanation of RECD operation similarly describes the device as an exhaust after-treatment system rather than an engine modification.

Aceget article on whether an RECD can reduce diesel exhaust odourFor a detailed discussion specifically focused on odour, the provides a deeper look at different smell sources and the situations in which an RECD is more or less effective.

Temperature Makes a Big Difference

An oxidation catalyst does not perform at its maximum immediately after a cold engine starts. It needs sufficient exhaust heat before oxidation reactions become effective.

This explains why a generator can still produce a noticeable smell during the first few minutes after starting even when an RECD is installed.

The same issue can occur when a generator operates for long periods at very light loads. Low-load operation can produce relatively cool exhaust, reducing catalyst activity. In contrast, normal loaded operation generally provides a better thermal environment for the after-treatment system.

Therefore, judging an RECD's effect on odour immediately after a cold start can give a misleading impression.

Which Smells Can an RECD Help With?

An RECD with an oxidation catalyst is most relevant when the odour comes from incomplete combustion products travelling through the exhaust.

For example, a strong oily or fuel-like exhaust smell may become less noticeable once the catalyst reaches operating temperature. Sharp or irritating odours associated with certain partial-oxidation products may also be reduced.

However, this does not mean that every smell around a generator will disappear.

The following distinction is useful:

Possible source	Can an RECD help?
Unburned hydrocarbons in exhaust	Yes, particularly with a warm oxidation catalyst
Some partial-combustion compounds	Yes
Soot-related exhaust emissions	The particulate section can help
Sulphur-related odour	Limited or no direct solution
Burning lubricating oil	No; investigate the engine
Fuel leakage	No; repair the leak
Fuel-tank or vent smell	No
Exhaust escaping before the RECD	No; repair the exhaust system

This is why identifying the source should come before assuming that an RECD is the answer.

What If the Smell Comes From Burning Oil?

A generator that consumes lubricating oil can produce a hot, burnt-oil smell that an RECD cannot fix at its source.

Possible causes can include worn piston rings, valve-seal problems, turbocharger issues, or excessive oil levels. In such cases, installing an emission-control device without addressing the underlying engine problem may leave the odour largely unchanged.

The same principle applies to visible smoke. Persistent smoke can indicate an engine, fuel-system, air-intake, or lubrication problem that deserves investigation rather than simply being treated as an emission-control-device issue.

Fuel Quality Also Matters

Fuel quality can influence exhaust characteristics. Sulphur-containing compounds, contaminated fuel, poor storage, and other fuel-related problems can contribute to unpleasant exhaust characteristics.

An RECD should therefore not be considered a substitute for appropriate fuel quality and engine maintenance.

CPCB's diesel-generator regulatory informationThe provides official information related to diesel-generator environmental requirements and should be consulted alongside applicable State Pollution Control Board directions.

For facilities using diesel generators regularly, maintaining proper fuel-storage practices and using appropriate fuel can help prevent avoidable combustion and odour problems.

What About Smell From Outside the Exhaust?

This is one of the most important points.

Sometimes people assume that an exhaust-treatment device is responsible for every diesel smell around a generator. But the smell may actually come from somewhere else.

Potential sources include:

Fuel-tank vents
Loose fuel connections
Fuel filters or lines
Oil leaks
Crankcase fumes
Spilled diesel
Oil-soaked insulation
Exhaust leakage before the RECD

If an exhaust flange leaks upstream of the RECD, untreated exhaust can escape before reaching the device. The RECD cannot clean exhaust that never enters it.

Likewise, if the smell is coming from a fuel tank or spilled diesel, changing the exhaust system will not solve the problem.

Does Reduced Odour Mean the Exhaust Is Safe?

No.

Smell is not a reliable measurement of overall exhaust safety.This distinction is extremely important.

A generator may produce less noticeable odour while still releasing gases and particulate emissions that require proper control and ventilation.

An RECD is an emission-control system, not a guarantee that exhaust can be discharged into an occupied space. Exhaust outlets must still be appropriately positioned and kept away from fresh-air intakes and occupied areas.

Central Electricity Authority's regulationsThe provide an official reference for broader electrical and generating-installation requirements, while environmental requirements should be checked with the applicable pollution-control authorities.

How Should You Evaluate Odour Improvement?

Instead of relying entirely on memory, compare operating conditions before and after installation.

Record:

Generator load
Operating duration
Whether the engine was cold or warm
Location where the smell was noticed
Type of odour
Weather and wind conditions
Any visible smoke
Whether the exhaust system has visible leaks

For example, if the smell is strong during a cold start but becomes considerably less noticeable after the generator reaches normal operating temperature, the behaviour may be consistent with temperature-dependent catalyst activity.

If the smell remains equally strong throughout operation, investigate the engine, fuel, exhaust joints, and other potential sources rather than assuming the RECD is ineffective.

Maintenance Still Matters

An RECD cannot compensate indefinitely for poor generator maintenance.

Dirty air filters, poorly maintained injectors, inappropriate loading, excessive oil consumption, and other engine problems can affect exhaust quality. A particulate filter can also accumulate soot and ash over time, making proper maintenance essential.

Aceget's technical material notes that RECD systems need to be correctly matched to generator exhaust flow, back-pressure limits, and installation geometry.

This is why a proper site assessment should consider the generator, exhaust system, operating load, and expected duty cycle together rather than treating the RECD as an isolated component.

Should Odour Reduction Be the Main Reason to Install an RECD?

Usually, no.

Odour reduction can be a useful secondary benefit, particularly where generator exhaust creates complaints around an operating site. But the primary reason for an RECD should be appropriate emission control and compliance with applicable requirements.

CPCB's published RECD framework is specifically concerned with emission reduction and certification rather than providing a universal odour-removal guarantee.

Therefore, anyone promising that an RECD will completely remove diesel smell should be asked for evidence and test conditions behind that claim.

A Practical Checklist

Before blaming or selecting an RECD for a diesel smell, check:

Is the smell definitely coming from the exhaust?
Does the smell reduce after the engine warms up?
Is the generator operating at an appropriate load?
Is there any fuel or oil leakage?
Are the injectors and air-intake system properly maintained?
Is the fuel clean and suitable for the engine?
Are there exhaust leaks before the RECD?
Is the RECD correctly matched to the generator?
Is back-pressure within the engine manufacturer's limit?
Is the exhaust outlet positioned correctly?

This approach helps distinguish an emission-control problem from an engine-maintenance or installation problem.

Conclusion

can an RECD for DG Set reduce diesel exhaust odour?So, Yes, it can reduce some odour-producing compounds, particularly unburned hydrocarbons and other partial-combustion products when an oxidation catalyst is operating at an appropriate temperature.

But an RECD is not an odour eliminator. It cannot correct fuel leaks, burning oil, poor fuel quality, exhaust leaks, fuel-tank vapours, or smells that originate outside the exhaust stream.

The best results come from treating the entire system as one: maintain the engine properly, use suitable fuel, operate the generator appropriately, inspect the exhaust installation, and select an appropriately matched RECD. Odour reduction can then be a useful additional benefit of a properly engineered emission-control system.

Can an RECD for DG Set Reduce Diesel Exhaust Odour? Understanding What It Can and Cannot Do

RECD For DG Set