October 28, 2026
Posted by: editor
Category: RECD & Emission Control Devices

On the asset schedule of a building sale, the generators get one line each: make, rating, year, “in working condition”. The retrofit emission control device bolted into each exhaust line may not appear at all. Whatever compliance liability it carries certainly does not.

That is what RECD due diligence is for. If you are buying a warehouse, office block, hotel, mall or factory shed in India, and especially in Delhi NCR, the DG sets and their RECDs are part of what you are paying for. This guide is a question bank, organised by the person you should be asking, followed by a document list, a red/amber/green table, a worked holdback example and a plan for your first 90 days of ownership.

This is not legal advice. Where consents, penalties or transfer procedures come up, the honest answer is “confirm with the State Pollution Control Board (SPCB) and your lawyer”.

Why the RECD matters in a property deal

Four risks connect the RECD to the deal value.

Sealing and enforcement risk

If an inspection finds a DG set operating without the required emission control, or without the paperwork to show the device is a type-approved model, the consequences can include directions to stop operating, sealing of the set and penalties. Our explainer on what happens when a DG set is sealed for non-compliance covers how disruptive that is. The new owner inherits the asset on the day of transfer.

GRAP operating limits in NCR

In Delhi NCR, the Commission for Air Quality Management (CAQM) issues directions on DG set use, including restrictions that tighten through the stages of the Graded Response Action Plan. Whether a set can run during higher GRAP stages can depend on its emission control status and fuel type. Our summary of GRAP rules for DG sets in Delhi NCR explains the general position; the current directions themselves should always be read from CAQM. A building whose sets cannot lawfully run in winter is a different asset from one whose sets can.

Replacement cost

An RECD is not a small consumable. If a device has to be replaced because its type approval cannot be shown, or because it is damaged beyond economical repair, the cost runs into lakhs per set before installation and testing. Our guide to RECD cost in India gives the factors that drive price.

Tenants who rely on backup

If the building is leased, tenants may have lease clauses about backup power availability. A sealed or GRAP-restricted DG set can turn into a service-level dispute with a tenant within weeks of completion.

A. Questions for the seller

Put these in the formal questionnaire so answers can be tied to warranties in the sale agreement.

How many DG sets are on the property, and which ones have RECDs fitted? A complete list matters because a “spare” set in a back yard can still count. A good answer lists every set with rating, serial number and RECD status, including sets that are rarely used.
Who supplied and installed each RECD, and when? The supplier’s identity decides whether you can get support, parts and certificate copies later. A good answer names the company, the date and the purchase order reference.
Can you provide the type approval certificate and test documents for each RECD model installed? Without these, you cannot show the device is an approved model for that engine range. A good answer is a copy of each certificate plus the supplier’s installation or commissioning report.
Whose name are the DG-related consents, registrations and permissions in? If they are in the seller’s company name, something has to happen on or after transfer. A good answer gives the exact names, reference numbers and validity dates.
Have any notices, show-cause letters, inspection reports or directions been received about the DG sets or air emissions? Outstanding matters may travel with the property. A good answer is “none”, supported by a written statement, or a full copy of each notice and the reply.
Has any DG set or RECD been replaced, relocated or modified since the RECD was fitted? Moving an RECD onto a different engine raises approval and suitability questions, explained in our post on whether an RECD can be transferred to another diesel generator. A good answer either confirms no changes or gives dates and records for each change.
Is there an active AMC or warranty for the RECDs, and can it be assigned? Transfer to a new owner is often silent in the contract. A good answer includes the documents, expiry dates and the supplier’s written view on assignment.
Are there any known faults, alarms or complaints about smoke, odour or noise from the DG area? Neighbour complaints often precede inspections. A good answer is honest and specific; vague reassurance is an amber flag.

B. Questions for the facility manager or O&M contractor

The people who run the plant room every day usually know more than the seller’s head office.

When was each RECD last serviced, and by whom? Service frequency is a proxy for how well the device has been looked after. A good answer points to a dated service report with the technician’s name and readings.
What differential pressure (ΔP) or backpressure readings do you record, and what was the baseline at commissioning? Where the design has ΔP monitoring, a reading well above baseline at similar load suggests loading or blockage. A good answer includes a log with dates, load and readings, not just “normal”.
Have there been any alarms, warning lights or controller fault codes in the last 12 months? If the RECD has a controller, its alarm history is evidence. A good answer includes the alarm log or photos of the display, with what was done about each one.
How many hours does each DG set run per month, and at what typical load? Running pattern affects how an RECD behaves, especially devices that need exhaust heat. A good answer comes from the hour meter and load logs, not memory.
Has the engine had any major repair, overhaul or injector work recently? Engine faults such as oil carry-over can load or damage a filter.
Where are the service reports kept, and are they complete? Reports with missing readings or no signatures are weak evidence. Our sibling post on auditing an RECD service report for missing information shows what a complete report should contain; ask for the last four and check them against it.
Have you ever run a set with the RECD bypassed or removed, even briefly? Any “yes” is a serious finding, because running without the device is a compliance risk regardless of the reason.

C. Questions for the RECD supplier, if reachable

Not every seller will let you contact the supplier before exchange, and some suppliers will not discuss a device with someone who is not yet the owner.

Can you confirm, from your records, the model and serial number supplied for each DG set at this address? Supplier records cross-check the seller’s list. A good answer matches serial numbers to engine ratings.
Is this model covered by a current type approval for the engine range it is fitted to? RECDs are type approved for defined ranges after testing by recognised agencies such as ARAI or ICAT. Our guide on how to verify a CPCB-tested RECD on a DG set explains the checks; ask the supplier to confirm the match in writing.
Can you reissue a copy of the certificate and the installation report if the seller has lost them? Many paperwork gaps are fixable if the supplier still holds records. A good answer gives a timeline and any fee.
Is the model still in production, and are parts and service available? A discontinued model is not automatically a problem, but it changes your risk. Our sibling post on planning parts and support when an RECD model is discontinued covers what to ask next.

D. Questions your own engineer should answer on site

A physical inspection is the core of technical due diligence for generator emission control. Send an engineer who knows DG sets and exhaust systems, with a checklist and a camera. Lockout/tagout applies whenever anyone opens panels or works near rotating or electrical equipment, following the site’s own permit system; the general principles are set out in OSHA’s guidance on the control of hazardous energy. Exhaust components stay hot long after shutdown, so plan any close inspection on a cold set.

Does the nameplate on each RECD match the paperwork, and is it legible? A missing or painted-over plate makes identification hard.
Is the RECD connected to the engine the paperwork says it is on? Trace the exhaust from manifold to RECD to stack.
Is there any bypass pipe, blanked flange, diverter or evidence of a removed section? A bypass route around the device is a major red flag. Photograph it.
What is the visible condition of the housing, insulation, flanges, bellows and supports? Look for cracks, soot streaks at joints, crushed insulation, rust and missing bolts. Soot tracks at a flange usually mean an exhaust leak.
With the set running at a stable load, what are the ΔP or backpressure readings, and how do they compare with the commissioning baseline? High backpressure affects engine performance and can indicate a loaded filter; our post on how exhaust backpressure affects a DG set explains why. Record load at the same time, because readings without load are hard to compare.
If the RECD has a controller, does it power up, and what does the display or log show? Check for active alarms, disabled functions or a dead screen. Photograph the screen.
Do the drawings on file match what is actually installed? As-built drawings are often out of date after modifications. Our sibling post on updating RECD drawings and records after exhaust modifications shows what a current record set should include.

E. Questions for your legal and EHS advisor

This is the part of RECD due diligence where you should not rely on engineers or on blog posts. Consent conditions differ by state and by type of establishment, and procedures change.

Which consents, registrations or permissions cover the DG sets, and do they transfer automatically on sale? In many cases a change of ownership has to be notified to, or approved by, the SPCB. Do not assume. Ask your advisor to confirm the current position with the relevant SPCB, and our general guide on getting pollution NOC for a DG set gives background on the documents usually involved.
What has to happen to change the name on the consent, and who is responsible for doing it? The sale agreement should allocate this task and its timing. Confirm the actual process with the SPCB.
Are there outstanding notices, directions or penalties attached to the premises or the DG sets? Your advisor may search records or ask the seller for a statutory declaration. Unresolved matters should be dealt with before completion or priced in.
What representations and warranties should the seller give about DG compliance? Typical areas include absence of notices, validity of consents and accuracy of documents provided. Your lawyer will draft these.
How will waste from RECD servicing be handled under your own EHS system? Rules on hazardous waste are administered through the SPCB; check with your EHS advisor and an authorised disposal partner rather than assuming a category.

The Central Pollution Control Board publishes the national RECD testing system and related documents; your advisor will usually read those alongside state-level consent conditions.

RECD documents for property purchase: the request list

Use the table below as the document request list in your data room.

Document	What it proves	Red flag if missing
Asset list of all DG sets with serial numbers	What you are actually buying	Sets you did not know about become your liability
RECD type approval certificate copy for each model	The device is an approved model for that engine range	You may not be able to show compliance at inspection
Supplier invoice and purchase order	Who supplied it and when	Hard to get supplier support or confirm authenticity
Installation and commissioning report with baseline ΔP	How it was fitted and what “normal” looked like	No reference point for judging current condition
Service reports for at least the last 12–24 months	The device has been maintained	Condition unknown; heavier inspection needed
ΔP, alarm and running-hour logs	Operating history between services	Faults may have been ignored
Consent, registration or NOC documents covering the DG sets	Legal authority to operate	Operating may be at risk after transfer
Inspection reports and any notices received	Enforcement history	Hidden outstanding matters
As-built exhaust and RECD drawings	What is installed and where	Modifications may be undocumented
AMC and warranty documents	Ongoing support and cost cover	Unplanned costs in year one

To read the certificate properly rather than just confirming one exists, see our guide on how to read an RECD test certificate. If the original DG set documents are also missing, the approach in specifying an RECD when original DG set documents are missing shows how engineers rebuild the engine data.

Red, amber and green: grading what you find

After the questions and the inspection, sort each finding into one of three bands.

Finding	Band	Typical response
Evidence of RECD bypass or removed device on a set that should have one	Red	Must be resolved before completion or priced as full replacement plus enforcement risk
No type approval certificate and supplier cannot be traced	Red	Price as replacement unless documentation is produced
Outstanding notice, direction or sealing order	Red	Resolve before completion or make it a condition precedent
Consent in seller’s name with no clear transfer route	Amber	Allocate responsibility and timeline in the agreement; confirm with SPCB
ΔP well above baseline at comparable load	Amber	Supplier diagnosis and service; price worst case
Certificate missing but supplier traceable and willing to reissue	Amber	Condition precedent or short holdback
Model discontinued but parts still available	Amber	Plan parts stock; include in asset plan
Complete documents, recent service, ΔP near baseline, no notices	Green	Normal handover; continue maintenance

A red finding need not kill a deal; it usually changes the price, timetable or structure.

How RECD due diligence findings feed the deal

The common tools are outlined here for general understanding only, not as legal advice; your lawyer will decide the right mix.

Price adjustment

The simplest approach is to reduce the price by the estimated cost of fixing the problems. It works best when the cost is fairly certain, such as a known service or a replacement quote.

Escrow or holdback

Where the cost is uncertain, part of the price can be held back, often in escrow, and released to the seller when defined conditions are met, such as delivery of a valid certificate or a satisfactory ΔP reading after service. The worked example below uses this approach.

Seller remedial obligations

The seller may agree to carry out specific work before completion, such as a full RECD service, reissue of documents or repair of exhaust leaks. Define the work, the acceptance test and who chooses the contractor. “Service the RECD” is not a specification.

Conditions precedent

Some items are serious enough that completion should not happen until they are cleared, such as an outstanding sealing order, or confirmation from the SPCB about the consent position.

Illustrative example: a warehouse with three DG sets

This example is illustrative. The costs are round figures chosen to show the method, not quotes for any model or site.

A buyer is acquiring a logistics warehouse in NCR. The site has three DG sets, each fitted with an RECD:

DG-1: 250 kVA
DG-2: 250 kVA
DG-3: 500 kVA

Due diligence produces two findings:

DG-2 (250 kVA): the seller cannot produce a type approval certificate for the RECD. The nameplate is partly legible. The supplier’s name is known but the company has not yet replied.
DG-3 (500 kVA): at a stable 60% load, the RECD ΔP reading is 70% above the commissioning baseline recorded at a similar load. Baseline was 8 kPa; today’s reading is 13.6 kPa (8 × 1.70 = 13.6). The last service report is 14 months old.

DG-1 is green: certificate on file, service six months ago, ΔP close to baseline.

Estimating the remediation cost

For DG-2, there are two outcomes. In the good case, the supplier reissues the certificate and confirms the model, at a nominal cost. In the bad case, the device cannot be shown to be approved and must be replaced. The buyer’s engineer uses an illustrative replacement budget:

RECD supply for 250 kVA: ₹4,50,000
Removal, installation and commissioning: ₹75,000
DG-2 worst case: ₹4,50,000 + ₹75,000 = ₹5,25,000

For DG-3, the likely cause is filter loading after a long service gap, but the engineer cannot rule out damage until the supplier inspects. DieselNet’s notes on ash in particulate filters explain what builds up over time. Again, two outcomes:

Good case: diagnostic visit ₹25,000 + cleaning and service ₹1,20,000 = ₹1,45,000
Worst case: diagnostic visit ₹25,000 + filter core replacement ₹4,00,000 = ₹4,25,000

The choice between servicing a core and replacing it is covered in our earlier post on filter core versus complete assembly replacement. For the size of set involved, the 500 kVA RECD page gives a starting point for supplier discussions.

The buyer also wants every set re-baselined and documented after completion:

Post-remediation check and documentation: 3 sets × ₹30,000 = ₹90,000

Building the holdback

The documentation cost is the buyer’s own operational cost, so the parties agree to deduct it as a straight price reduction of ₹90,000. The two uncertain findings are handled through a holdback, each at its worst-case cost plus a 10% contingency:

DG-2: ₹5,25,000 × 1.10 = ₹5,77,500
DG-3: ₹4,25,000 × 1.10 = ₹4,67,500
Total holdback: ₹5,77,500 + ₹4,67,500 = ₹10,45,000

Tranche	Amount	Released to seller if	Otherwise used for
DG-2 certificate	₹5,77,500	Supplier confirms model and reissues certificate within 60 days	Replacement RECD for DG-2
DG-3 condition	₹4,67,500	Service brings ΔP back within 15% of baseline at comparable load	Diagnosis, core replacement and retest

Total effect on the seller’s proceeds at completion: ₹90,000 price reduction + ₹10,45,000 held = ₹11,35,000 not paid on the day.

What happened next

In this illustration, the supplier replies within three weeks, confirms the DG-2 model and reissues the certificate for a small admin fee. The ₹5,77,500 tranche is released. DG-3’s service brings ΔP back to 8.8 kPa at similar load, which is 10% above baseline (8 × 1.10 = 8.8), inside the agreed 15% band. The cleaning and service cost ₹1,45,000, paid from the second tranche, and the remaining ₹4,67,500 − ₹1,45,000 = ₹3,22,500 is released to the seller.

The seller was paid for an asset that proved to be in reasonable shape, and the buyer never carried the risk while that was being proven.

Your first 90 days after purchase

Completion is when the compliance responsibility shifts. Use the first three months to turn inherited paperwork into your own system.

Days 1–30: take control

Confirm who now holds the consent and that any required notification or application to the SPCB has been made, in the form your advisor agreed.
Assign or replace the AMC so that someone is contractually responsible for the RECDs from day one.
Brief operators on the RECD basics for each set, including what alarms mean and who to call.
Photograph every RECD nameplate, ΔP gauge or display, and stack under load, and file the photos with dates.

Days 31–60: establish a baseline

Arrange a full service on any set without a recent report, by the supplier or a contractor they have approved.
Record ΔP at defined loads after service to create your own baseline. Use one date format across all logs so day and month are never confused.
Close any remedial items the seller agreed to and confirm holdback release conditions with evidence.
Set up a register for each set: engine data, RECD model and serial, certificate reference, service dates, readings and alarms. The general RECD maintenance guide is a useful reference for what to log.

Days 61–90: plan ahead

Check the current GRAP directions and decide how the building will manage backup power in winter.
Budget for the next 12 months of RECD service and any parts at risk of obsolescence.
Update drawings and the site’s compliance file so the next inspection, or the next buyer, finds a clean record.

If you are buying residential or mixed-use property where an RWA will take over, the checks overlap heavily with our sibling guide on RECD handover from a developer to an RWA.

FAQ

What is RECD due diligence in a property purchase?

It is the set of checks a buyer carries out on the DG sets and their retrofit emission control devices before buying a building. It covers documents, physical condition, operating history, consents and outstanding notices, so the buyer knows what compliance liability comes with the property.

Does the DG set consent transfer automatically when a building is sold?

Do not assume it does. Consent rules and procedures for change of ownership vary by state and type of establishment. Ask your legal or EHS advisor to confirm the current requirement with the relevant SPCB, and allocate the task in the sale agreement.

What if the seller cannot find the RECD certificate?

Try the RECD supplier first, since many suppliers can reissue copies from their records. If the device cannot be traced to an approved model, treat it as a significant risk and price it as possible replacement, often through a holdback.

Can a high differential pressure reading be fixed easily?

Often a service or cleaning brings ΔP back towards baseline, especially after a long service gap. Sometimes it indicates damage or engine-side problems. Get the supplier to diagnose it before you assume the cheaper outcome.

Need Help Checking the RECDs in a Building You Are Buying?

Aceget supplies CPCB type-approved retrofit emission control devices for DG sets from 25 kVA to 2500 kVA. If you are evaluating a property and need help assessing an existing device, planning remediation or replacing an RECD that cannot be documented, our team can help. Review our certifications and contact us with the DG nameplate details and photos of each RECD.

Buying a Building with an Existing RECD: Due Diligence Questions