CPCB II, CPCB IV+ and RECD are not three versions of one rule — they are three separate regimes that bind different gensets. CPCB IV+ applies to new gensets up to 800 kW sold since 1 July 2023; sets already installed are not retro-bound by it; an RECD is a retrofit for existing sets, required only where a regional rule demands it. Three questions settle which one binds yours: what you own, what you are buying, and where it runs. (You will see the stages written both ways — CPCB 2 and CPCB II, CPCB 4+ and CPCB IV+. Same stages, same rules.)
TL;DR
- CPCB IV+ — the emission standard for new gensets up to 800 kW: G.S.R. 804(E) of 3 November 2022, in force since 1 July 2023
- CPCB II — the previous stage (G.S.R. 771(E) of 2013). Nothing in the CPCB IV+ gazette orders an installed CPCB II set retired or retrofitted
- RECD — a CPCB-certified retrofit (minimum 70% particulate capture) for existing sets, mandatory only where a regional regime says so: Delhi-NCR, Maharashtra and Karnataka today
- Above 800 kW — outside all three; the MoEFCC’s separate large-engine rules (G.S.R. 489(E), 2002) govern
- The decision table below settles most cases; the compliance hub takes you from “which regime” to “what now”
Three terms, three different jobs
CPCB II is an emission stage — the norms notified by G.S.R. 771(E) of 11 December 2013, applying to genset engines manufactured or imported from 1 July 2014. If your set was bought new between 2014 and mid-2023, it is almost certainly a CPCB II machine. It was legal when sold, and the stage it was certified to travels with it for life.
CPCB IV+ is the stage that replaced it — notified by G.S.R. 804(E) of 3 November 2022, in force from 1 July 2023 for new engines and gensets up to 800 kW. It is a point-of-manufacture-and-sale rule: it decides what may be built, imported and sold, not what may keep running. What the norms actually demand — the limits, the five power bands (the smallest covers engines of 8 kW and below), the certification chain — is unpacked separately in CPCB IV+ norms, explained.
RECD is not a stage at all. A Retrofit Emission Control Device is a certified exhaust bolt-on for existing sets — CPCB’s procedure requires at least 70% particulate capture — and it exists because regulators needed a middle path between letting old sets run as-is and forcing replacement. No pan-India rule requires one; three regional regimes do.
Three instruments, three verbs: CPCB II describes the set you own, CPCB IV+ governs the set you buy next, and an RECD rescues an existing set where a regional rule has caught up with it.
The decision table
Find your row:
| What you own / are buying | Where it runs | Which regime binds | What that means |
|---|---|---|---|
| New set, up to 800 kW | Anywhere in India | CPCB IV+ — G.S.R. 804(E), in force 1 July 2023 | Only factory-certified CPCB IV+ sets may be sold. No small-set exemption |
| New set, above 800 kW | Anywhere in India | Not CPCB IV+ — MoEFCC large-engine rules, G.S.R. 489(E) | A different emission, stack and consent regime; engineered case by case |
| Existing set | Delhi-NCR | CAQM Direction No. 76 | Dual-fuel conversion and/or a CPCB-certified RECD by capacity band; GRAP usage bans; CAQM is sealing violators |
| Existing set, up to 800 kW | Maharashtra | MPCB circular of 2 June 2023 | RECD on qualifying in-use sets state-wide; the window closed 31 December 2023 — now enforced through consent conditions |
| Existing set, 125 kVA and above | Karnataka | KSPCB notification of 25 May 2023 | RECD mandatory at 125 kVA and above; smaller sets live under consent conditions |
| Existing set | Anywhere else | Your consent to operate | No blanket retrofit mandate as of 1 August 2026 — obligations live in your SPCB consent conditions |
| Set made and installed before 1 July 2004, or meeting no notified stage | Anywhere | CPCB’s RECD procedure: scrap | Such engines are to be scrapped — not sold, not used, not run. No RECD can save them |
Two things the table quietly settles. First, the regime follows the transaction and the territory, not the sticker on the canopy — the same CPCB II set faces no retrofit mandate across most of India, a state-wide circular in Maharashtra, and usage bans plus sealing risk in Delhi-NCR. Second, CPCB IV+ appears in exactly one row. It is a purchasing rule. Everything that touches an already-installed set comes from CAQM, a state board, or your consent letter.
“Is my CPCB II set now illegal?”
No — and this confusion drives a good share of the compliance calls we take. G.S.R. 804(E) states its scope in its first operative line: emission limits for new engines used for genset applications up to 800 kW. It controls manufacture, import and sale from 1 July 2023, and its own transition clauses let manufacturers build gensets to the earlier norms until 31 December 2023. Nothing in it orders an installed set retrofitted, upgraded or retired.
Our own fleet is the honest example: the 62.5 kVA Cummins set on our rental ladder is a CPCB II machine, and it remains legal to operate and to rent in most states, subject to state pollution-board conditions. Where a retrofit regime does bind — Maharashtra’s MPCB circular is the exception closest to home for us — the obligation comes from that circular and the site’s consent conditions, not from CPCB IV+, and where a consent demands a IV+ set we deploy one instead.
What nobody can do is sell you that CPCB II set as new. New sales up to 800 kW are CPCB IV+ only — which is why the CPCB IV+ ratings from 82.5 kVA upward in our fleet carry SCR after-treatment and a DEF tank, and why the step-change is real: Cummins put the reduction at roughly 90% lower PM and NOx than CPCB II when it launched the compliant range.
What an RECD actually certifies — and what it doesn’t
The retrofit path has its own paperwork, and it is stricter than most vendors let on:
- The origin is a tribunal order. The NGT (O.A. No. 681/2018, order dated 6 August 2019) directed CPCB to set norms for retrofit devices with a minimum 70% PM capture efficiency on in-use DG sets below 800 kW. CPCB’s procedure PCLS/12/2021-22 is the result, and it applies to engines that have completed five years from their date of manufacture.
- Devices are certified by engine phase and power band. Phase I covers engines built to the 2002 norms (manufactured or imported 1 July 2004 to 1 July 2014); Phase II covers CPCB II engines (on or after 1 July 2014). A device certified for a Phase II engine of 110–250 kW is not certified for your Phase I 300 kW one.
- Only listed devices count. CPCB publishes the certified-manufacturer list — fourteen manufacturers as of 30 June 2026, Chakr Innovation, Pi Green and Cummins Technologies among them — each entry tied to an exact kW range and phase. An uncertified “smoke filter” achieves nothing legally.
- An RECD is PM capture, not a stage upgrade. The certification tests particulate reduction; other gaseous emissions must simply not rise above the engine’s baseline. A retrofitted CPCB II set satisfies the retrofit regime that demanded it — it does not become, and can never be sold as, a CPCB IV+ set.
We have run this retrofit evaluation on client sets — including a 625 kVA Perkins unit — with certified vendors, and the recurring lesson is matching: the device must be certified for your engine’s phase and kW band, and the retrofit-versus-replacement arithmetic must be run before anyone bolts anything on. That arithmetic is the compliance hub’s territory.
The edge cases worth naming
- Above 800 kW, none of the three applies. A 1010 kVA set has no CPCB IV+ certificate and no RECD path — it sits under the MoEFCC’s 2002 rules for large engines, with its own stack regime. The six 1010 kVA sets we installed for the Reserve Bank of India — delivered with three 30-metre stacks across three sites — live entirely in that world.
- Noise and stack rules cut across all three. The 75 dB(A)-at-1-m limit and the stack-height guideline predate CPCB IV+ and survive it. A brand-new IV+ set with a short stack is still a non-compliant installation.
- The regimes move at different speeds. Which regime applies is stable; how hard it bites is not. CAQM’s November 2025 GRAP revision moved DG restrictions a full stage earlier, its sealing list was updated as recently as July 2026, and Maharashtra has shifted from a dated compliance window to enforcement through consent conditions.
The one-line version
Buying new up to 800 kW: CPCB IV+, no exceptions. Running an existing set: nothing changes until Delhi-NCR, Maharashtra, Karnataka, Kerala or your consent letter says it does — and when it does, the answer is usually an RECD, chosen from CPCB’s certified list and matched to your engine’s phase and band. Send the nameplate photo on WhatsApp and we will tell you which row of the table you are in — or start with the compliance hub and its sixty-second checker.
Sources: G.S.R. 804(E) of 3 November 2022, MoEFCC (CPCB IV+ scope, commencement and transition dates), read in full; CPCB, System and Procedure for Emission Compliance Testing of RECD, PCLS/12/2021-22, revised 24 July 2023 (70% PM capture, Phase I/II definitions, five-year applicability, scrap rule for pre-2004 engines); CPCB list of certified RECD manufacturers as of 30 June 2026; CAQM Direction No. 76 for Delhi-NCR (via PIB, 29 September 2023); MPCB circular of 2 June 2023 (window extended to 31 December 2023 by circular of 26 October 2023); KSPCB notification of 25 May 2023; G.S.R. 489(E) of 9 July 2002 for engines above 800 kW. The primary documents are linked from the compliance hub’s sources section. State consent conditions prevail over everything here — confirm your site’s position with your SPCB.