RECD for Food Processing Units: Planning Exhaust Work Near Production Areas

In most factories, fitting a retrofit emission control device is an engineering job. In a food plant, the same job sits a few metres from product that people will eat, and every spark, flake of rust or loose bolt has a route into a production hall if nobody plans for it.

This guide treats an RECD for food processing units as what it really is: a food safety project with an engineering core. We will walk the site from the generator yard inwards, look at where exhaust ends up, and then build a hazard control table in the same spirit as the prerequisite programmes your QA team already runs. The aim: a compliant DG set and nothing for your auditors to worry about.

Why Exhaust Work Is a Food Safety Issue, Not Only an Engineering Job

A food business operator is responsible for what reaches the product, whatever the source. If a metal sliver turns up in a batch of namkeen, the complaint lands on your brand, not on the fabricator.

Retrofit work brings a specific set of contaminants close to a food site:

• Soot and carbon flakes from inside old exhaust pipes, which break loose when a line is opened or tapped.
• Metal swarf and grinding dust from cutting, drilling and dressing flanges.
• Weld spatter and slag, which can travel further than people expect.
• Paint and primer fumes from touching up supports and new sections.
• Insulation fibre from lagging removed or replaced around the hot section.
• Pests, because opened wall sleeves, removed panels and propped doors give rodents and birds new routes in.
• Glass and brittle plastics from torch lenses, phone screens, gauge covers and safety glasses.
• Odour taint, which is the one engineers often forget.

Odour deserves a sentence of its own. Fat-rich products pick up smells easily. Ghee, butter, cream, chocolate, bakery shortening and edible oils can absorb diesel and solvent odours from the air around them. A batch can be microbiologically perfect and still be rejected because it smells faintly of exhaust or fresh paint.

There is also the matter of dust spreading across lines. Allergen control is not usually the main risk in exhaust work, but grinding dust and disturbed debris can carry existing residues from one area into another. If a crew walks from a peanut line to a plain biscuit area with dusty boots, your allergen plan has been bypassed without anyone noticing.

Walking the Site: From the DG Yard to the Cold Rooms

Walk the job with the contractor, your maintenance lead and your QA head. Start at the DG yard and move inward. Zone names vary between sites and certification schemes, but the logic is the same: the closer you get to exposed, ready-to-eat product, the tighter the controls.

Zone Map and Allowed Work

Zone	Typical Areas	Exhaust Work Allowed?	Key Controls
Outer yard	DG yard, fuel store, scrap area, parking	Yes, main work zone	Hot work permit, fire watch, spark screens, housekeeping at end of each shift
Receiving	Raw material dock, weighbridge	Only routing of materials, no cutting	Keep dock doors shut while cutting outside, separate contractor material path
Dry stores	Flour, sugar, spices, packaging stock	No work; access only if exhaust passes through	Sheet and seal stacks, move pallets away, pest check after
Low-risk processing	Washing, sorting, raw handling	Only with QA approval and enclosure	Temporary enclosure, product removed, line covered
High-care / high-risk	Post-cook, ready-to-eat, filling, chilled assembly	Avoid entirely during production	Work only at shutdown, full change of clothing, swab release
Packing	Primary packing, form-fill-seal	Avoid; secondary packing only with QA sign-off	Cover open film reels, remove loose packaging
Finished goods	Dispatch store, ambient warehouse	Limited, if exhaust route crosses	Shrink-wrapped pallets only, no open cartons nearby
Cold rooms	Chillers, freezers, ripening rooms	No work inside; check external walls and condensers	Keep doors closed, watch for exhaust drawn into condenser intakes

In most plants, the RECD sits in the outer yard, so most cutting and welding happens outside. The risk comes from the bits that cross zones: an exhaust pipe that runs along an internal wall, a wall sleeve into a DG room inside the main building, or a rooftop discharge above a packing hall. Mark each of these on your walk.

At each stop, note what the crew will carry, which openings will be made, what product is nearby, how air moves and who from QA owns the zone. That marked-up plan becomes the backbone of your method statement and the first page of your audit record.

Where the Exhaust Ends Up

The DG set’s discharge point matters as much as the work itself. A food plant can have a perfectly clean retrofit and still have a standing problem if exhaust drifts into the building every time the set runs.

Check these points during the walk:

• Discharge height and direction. Is the stack outlet above the roofline of nearby buildings? Does it point away from the main building or straight at it?
• Air intakes. Note every fresh air intake, AHU louvre and make-up air unit. Food plants often run high-care rooms under positive pressure, which means they pull large volumes of outside air. If that air comes from near the DG stack, the filters are doing your exhaust’s job.
• Open dock doors. Receiving and dispatch docks are often open for long spells. Exhaust that pools near a dock will reach the stores.
• Prevailing wind. In much of NCR, winter winds tend to come from the north-west, and calm, inversion-prone days trap exhaust near the ground. Check your own site; local buildings change everything.
• Cold room condensers. Condensers pull large volumes of air. Exhaust heat and soot near a condenser can reduce efficiency and dirty the coils. For cold chain operations, see the NCCD basic data sheets for context on how cold chain infrastructure is planned.

If any of these look poor, the retrofit is the right moment to fix them. Extending a stack, turning the outlet or adding a rain cap with the right orientation can be done while the line is already open, provided the extra length and bends stay within the engine maker’s backpressure limit. Our guide on how exhaust backpressure affects a DG set explains why this check cannot be skipped.

How an RECD Changes the Picture, and What It Does Not

An RECD is an emission control device, not a food safety device. But it has side benefits for a food plant.

What It Can Change

A typical RECD combines a diesel oxidation catalyst (DOC) with a diesel particulate filter (DPF). The DPF traps soot that would otherwise leave the stack. Aceget’s RECD uses a silicon carbide DPF with a precious metal coating and claims around 96% PM reduction, though the real figure depends on the DG set’s condition and the fuel used. For a food site, less visible soot means less black deposit on roofs, gutters, louvres and intake filters.

The DOC oxidises some hydrocarbons and carbon monoxide. Many users report less diesel smell after fitment, but odour is a complex mix and results vary with engine health and load. We have covered this in detail in can an RECD reduce diesel exhaust odour. Treat odour improvement as a possible benefit, not a promise.

What It Does Not Change

• Discharge location. If the stack points at an air intake, an RECD will not move it.
• Heat. The exhaust is still hot, and so is the RECD housing.
• NOx. A DOC plus DPF system is not designed as a NOx reduction device.
• Poor engine condition. A set burning oil or running rich will load the filter faster. Fix the engine first.

One more point: passive DPF regeneration needs the exhaust to get hot enough, which usually means running at a meaningful load, often cited as around 40 to 50% or above depending on design. Many food plants run DG sets only during outages, sometimes on light load. If your set mostly idles through short cuts, read is an RECD suitable for a DG set that runs only occasionally and discuss load testing with your supplier.

Hazard-by-Hazard Control Table

This mirrors how prerequisite programmes are written: hazard, source, control, and how you prove the control worked.

Hazard	Source During Retrofit	Control	Verification
Physical: metal swarf, slag	Cutting, grinding, welding exhaust line	Work outside where possible; spark and swarf screens; magnetic sweep of the area	Visual check plus magnetic sweep log signed by supervisor
Physical: soot and rust flakes	Opening old exhaust pipes and sleeves	Cap open pipe ends immediately; bag removed sections on site	Inspection of floors, ledges and nearby equipment before release
Physical: glass and brittle plastic	Torches, phones, gauges, safety glasses	Glass and hard plastic register; only listed items allowed	Count items in and out against the register
Physical: loose fasteners and tools	Bolts, washers, drill bits, cable ties	Tool register; parts kept in closed trays	Tool count at end of each shift
Chemical: paint and primer fumes	Touch-up of supports and new sections	Do painting outdoors, off-shift, using low-odour coatings; allow curing time	Odour check by QA before doors reopen
Chemical: sealants, solvents	Flange assembly, cleaning	Approved chemical list; store outside production zones	Checked at gate by QA
Chemical: diesel and exhaust odour	Test runs during commissioning	Run tests with dock doors closed and intakes checked	Sensory check in nearest product area
Biological: pests	Opened sleeves, removed panels, propped doors	Seal openings at end of each shift; no doors left open	Pest control contractor inspection after work
Biological: contamination from people	Contractor clothing, hands, footwear	Induction, hygiene rules, clothing and footwear change	Supervisor check at zone entry
Cross-contamination: dust spreading	Movement of crew and material between areas	Fixed contractor route; no crossing between lines	Route walked and checked by QA

Tick off each verification and attach the table to the permit pack.

Contractor Management in the Spirit of FSSAI Schedule 4

FSSAI’s Schedule 4 sets out general hygienic and sanitary practices for food businesses, covering premises, personal hygiene, pest control, cleaning and training. It does not have a chapter titled “exhaust retrofits”, but its intent clearly reaches anyone who enters your food handling areas. You can read the FSSAI Schedule 4 requirements published by the Delhi Food Safety Department and map them onto your contractor rules.

Before the Crew Arrives

• Share hygiene rules, glass policy and zone map with the supplier in writing.
• Get crew names and confirm none has a reportable illness.
• Agree the tools, chemicals and materials that will come in, and who acts as fire watch.

On Day One

Run a short induction covering:

1. Zone boundaries and off-limits areas.
2. Handwashing points.
3. Hairnets, clean overalls, and overshoes or dedicated footwear for internal areas.
4. No eating, gutka, tobacco or smoking except in designated spots.
5. No jewellery or loose items in top pockets.
6. Glass policy, tool register and how to report breakages or spills.

Record attendance with signatures.

During the Work

A named supervisor from your side should stay with the crew whenever they are inside or near openings. Fabricators know metal work, not which door must never be left ajar during a run.

Hot work in a food plant needs special care. Flour, sugar, spice and milk powder are combustible dusts, and oil and packaging stores often sit near utilities. A hot work permit, trained fire watch, extinguishers and a post-work check are the minimum.

Timing the Work Around Production

A two-day shutdown at the wrong time can cost more than the RECD itself.

Seasonal Peaks to Avoid

• Mango pulp season, usually summer into early monsoon, when pulp plants may run close to round the clock.
• Dairy flush season, when milk procurement peaks after the monsoon and into winter, and plants are converting surplus into powder, butter and ghee.
• Festival sweets peak around Diwali, when mithai, dry fruit and gifting packs are in full swing.
• Summer demand for ice cream and beverage units.

There is an NCR-specific complication. The Diwali production peak overlaps with the start of the winter pollution season, when GRAP stages are often invoked. Under GRAP, DG use can be restricted except for emergency and essential services. In October 2023, reports listed essential services such as hospitals, elevators and water pumping among those allowed to run DG sets, as covered by India Gazette’s report on DG sets allowed for emergency services. Food processing may or may not fall within the categories allowed at a given stage, so check the current GRAP schedule and CAQM direction for your sector. Our post on GRAP rules for DG sets in Delhi NCR gives the background.

The practical lesson: if your DG set needs an RECD to keep running through winter, plan the retrofit for the lean months before the peak, not during it.

Using Planned Downtime

1. Weekly sanitation shift: fine for survey and measurement, not for cutting near the building.
2. Maintenance days: often the best slot for fitment.
3. Annual shutdown: ideal if the exhaust passes through the building or over high-care rooms.

The RECD installation process usually runs from survey and nameplate photos through design, fabrication, fitment, commissioning and testing. DG downtime for fitment is often a day or two per set, though this varies. Survey and fabrication happen before the shutdown, so the blocked window can be short.

Sending clear DG nameplate photos for an RECD enquiry can save a survey visit, and one fewer contractor through your gate.

Isolation Steps During the Work

• Cover openings. Seal louvres, vents and wall sleeves near the work with heavy-duty polythene and tape.
• Build temporary enclosures. For any internal work, erect a sheeted enclosure from floor to ceiling, with a single entry point and a mat or tacky sheet at the door.
• Manage air pressure. If work happens inside, consider a portable extractor to keep the enclosure under slight negative pressure relative to the production area. Exhaust from that extractor must go outside, away from intakes.
• Sheet equipment and product. Remove product where possible. Cover anything that cannot be moved, including conveyors, hoppers and open packaging reels.
• Seal drains. Cover floor drains in the work area so swarf, slag and debris do not enter the drainage system, where they can create blockages or pest harbourage.
• Close dock doors during cutting, and bring parts in through the yard, not the factory.

If your exhaust line is long and passes through sensitive areas, ask your supplier whether a flanged connection is possible. Our post on whether an RECD can be installed without cutting the existing exhaust pipe covers when this works and when it does not.

After the Work: Cleaning, Checks and Release to Production

The job ends when QA signs the area back into production, not at the test run.

Cleaning Verification

• Fold sheeting inward as you remove it.
• Vacuum, then wet clean. Avoid dry sweeping.
• Clean ledges, cable trays and equipment tops; check nearby AHU pre-filters.

Microbiological and Hygiene Checks

If your site programme uses ATP swabs or microbiological swabs, take them from food contact surfaces in any zone that was opened or affected. Use your existing limits.

Pest Inspection

Your pest contractor should confirm every sleeve and gap is sealed and moved bait stations are back in position.

Release Sign-off

The release form records areas affected, reconciled tool and glass counts, cleaning and swab results, pest inspection, the closed hot work permit and a QA signature. No signature, no production.

Record Keeping for Audits

Food plants face several types of audit: FSSAI inspections, customer audits and certification audits under schemes such as FSSC 22000 or BRCGS. All of them will want to see that contractor work was planned and controlled.

Keep in one file: method statement and site plan, the hazard control table, induction records, hot work permits, tool and glass registers, cleaning, swab and pest records, the QA release form, and the RECD’s test certificates and CPCB type approval references.

On the pollution side, keep the RECD paperwork alongside your consent documents. The CAQM Direction No. 76 of 29 September 2023 set out the NCR framework: DG sets of 19 to 125 kW to move to dual fuel, 125 to 800 kW to use dual fuel or an RECD, and above 800 kW to use an RECD. Rules can change, so confirm the current direction and your SPCB’s requirements. Aceget’s RECD carries CPCB type approval under system procedure PCLS/12/2021-22 and is aligned with Direction 76.

Plan RECD upkeep into your engineering schedule so filter checks never become unplanned visits mid-run. Our RECD maintenance guide covers the routine.

Illustrative Profiles: Three Food Units

These are composite, illustrative examples to show how planning changes with site type. They are not real customers.

Small Bakery Unit, 62.5 kVA

A bakery on an industrial plot runs a single 62.5 kVA DG set in a small yard next to the dispatch dock.

Planning points (illustrative): At 62.5 kVA, which is roughly 50 kW, this set falls in the band where dual fuel was the stated route under Direction 76, so the owner should check which option applies. If an RECD route is chosen or permitted, the main risk is the stack’s closeness to the dispatch dock, where open bread trays sit. The fitment is scheduled on the weekly off day, with the dock shuttered and trays moved inside. Fat-rich products like cakes and shortening stock are moved away from the dock wall to reduce odour risk during test runs.

Dairy Plant, 2 x 625 kVA

A milk processing plant with two 625 kVA DG sets in a separate DG house, about 30 metres from the main process building. The plant makes pouch milk, curd, butter and ghee.

Planning points (illustrative): The two sets are retrofitted one at a time, so one set always covers chilling and pasteurisation during an outage. The work is booked for the lean season before the flush. The DG house stack sits upwind of the butter room’s air intake in winter, so the stack is extended during the retrofit, with backpressure recalculated. QA treats butter and ghee areas as odour-sensitive and runs a sensory check after commissioning tests.

Spice and Snack Unit, 320 kVA

A unit grinding spices and frying namkeen runs a 320 kVA DG set whose exhaust passes through an internal wall sleeve and up the side of the building.

Planning points (illustrative): Spice dust is combustible, and frying oil is stored nearby, so the hot work permit includes a wider exclusion zone and a longer fire watch. The internal wall sleeve is handled inside a sheeted enclosure under negative pressure. Grinding stops completely during fitment because the dust load in the air is high. The pest contractor seals and checks the wall sleeve after the work, since that gap was a known rodent route.

Frequently Asked Questions

Is an RECD for food processing units different from one for other factories?

The device is the same type. What changes is the planning: zone controls, contractor hygiene, timing and QA release.

Can RECD installation be done while the food plant is running?

Survey and outdoor preparation often can, if openings stay closed. Cutting, welding and test runs near sensitive areas belong in a planned shutdown.

Will an RECD stop diesel smell entering our production hall?

It may help. The DOC treats some odour-causing compounds and the DPF reduces soot. However, the discharge position, wind and air intakes matter just as much. If exhaust is being drawn into the building, fix the stack location as well.

Does FSSAI require specific rules for contractors doing exhaust work?

FSSAI Schedule 4 sets general hygiene and sanitary practices for food businesses. It does not name exhaust retrofits, but its principles on personal hygiene, pest control, cleaning and premises apply to anyone entering food areas. Build your contractor rules on it.

How long does the DG set stay out of service?

Fitment often takes a day or two per set, though this varies with the exhaust route and site access. Survey and fabrication happen beforehand.

What records should we keep for an FSSC 22000 or BRCGS audit?

Everything listed in the record keeping section above, filed together with the RECD’s certificates.

Planning Your Food Plant Retrofit

An RECD project in a food plant succeeds when engineering and QA plan it together. Walk the site, map the zones, check where the exhaust goes, and turn every hazard into a control with a clear way to verify it. Done this way, the retrofit becomes one more controlled maintenance job rather than a risk to product.

If you are planning an RECD for a food processing unit in NCR, Aceget can carry out a site survey with your maintenance and QA teams, recommend the right model for your DG set, and work within your hygiene rules and shutdown windows. Read more about our retrofit emission control device range or contact us to book a survey.