Industry hazard classes under NBC 2026 and what each kind needs

NBC 2026 sorts industries into three groups by how easily and how fiercely their materials burn: G1 low hazard, G2 moderate hazard and G3 high hazard, with G3 split into A and B. The group sets how strict the fire rules are. In Table 7G of Part F, a low hazard unit of up to 1,000 sq m is asked only for extinguishers and hose reels, while a high hazard unit is asked for sprinklers at every size. A separate annex, marked informative, then suggests tanks, pumps and special systems for named industries. The standard is voluntary until a state adopts it through its byelaws or its Fire Act. This is an extra chapter in our series on the 2026 national building standards. Checked 15 November 2026.

In short

• Three classes: Annex B lists industries under G1 low, G2 moderate and G3 high hazard. G3 has a sub-category A and a heavier sub-category B.
• The class sets the rules: Table 7G asks for more installations as the class and the built-up area go up. Annex K also uses the class to size roof vents.
• Annex N is advice, not a rule. It is printed as informative. It suggests what each kind of industry should have, with water tank and pump sizes for smaller units.

Who this chapter is for

Owners and managers of factories, mills and godowns, and the neighbours of an industrial estate. It adds to our chapter on factories, godowns and hazardous industries. This one asks which class your industry is in, and what the class asks for.

Where the classes come from

Clause 3.1.8 of Part F points to Annex B, a broad classification of industrial occupancies by degree of fire hazard. It has three columns, G1, G2 and G3, and lists trades one per line. Two notes sit under the list. An occupancy that is not covered should be placed in the most appropriate class that resembles it. And for classes based on chemical hazard or pollution, state or central guidelines should be read. Table 7G uses the same classes, written G-1, G-2 and G-3. We read all four pages from the page images. The examples below are only a few lines of each column.

G1, low hazard

In plain words, these are trades where the materials are not easy to ignite or the process does not pile up fuel. Printed examples include breweries, brick works, engineering workshops, dairies, pottery works, garages and godowns storing non-combustible goods only.

G2, moderate hazard

These are trades with ordinary combustible materials in useful quantity: grain, paper, cloth, plastic, wood. Printed examples include rice mills, flour mills, plastic goods manufacturing, textile mills, printing press premises, bakeries and biscuit factories, pharmaceuticals and cold storage premises. So do godowns of the in-between kind and a kitchen with live cooking.

G3, high hazard

These are trades with flammable liquids, dust, fine fibre, explosives or heavy stocks of plastic or oil. Sub-category A printed examples include saw mills, paint and varnish factories, spray painting, fireworks and match factories, oil mills, jute mills, foam plastics and godowns storing combustible or flammable goods. Sub-category B holds the heaviest risks: explosive factories, LPG bullets, ammonia and urea synthesis plants and above-ground oil storage.

A note on layout: the sub-heading (A) is printed once, on the first page, and (B) once, on the third, so items between them sit under A by position only. A note at the foot says that where a complex has separate plants of different hazard, the authority having jurisdiction should be consulted on the level of protection.

Where the class surprises people

• A room in an office can be G3. A server room, a UPS room with batteries, a battery room with lithium-ion batteries and a diesel generator room are all in the high hazard column.
• Oxygen plants are printed in the G2 column, not with the heavier plants. That is as printed.
• A godown can be G1, G2 or G3, depending on what it holds.

What the class changes

In the Table 7G rows we read from the page images, a low hazard unit up to 1,000 sq m, MSMEs included, is asked for extinguishers and hose reels and nothing more. A moderate hazard unit is first asked for sprinklers above 3,001 sq m. A high hazard unit is asked for them in every row, from the smallest, up to 250 sq m. If the unit keeps combustible storage or packing, fuel or boilers, note 1 says those areas should be protected at the CL-6 level, a combined sprinkler and hose-stream level.

The class also sizes roof vents. Annex K covers single-storey industrial buildings with large undivided floors and asks for automatic vents in industrial buildings of medium hazard or above with a floor above 750 sq m. The ratio of vent opening to floor area is 1 to 150 for G-1, 1 to 100 for G-2 and 1 to 30 to 1 to 50 for G-3. Vents are not to depend on electric power. Our chapter on roof smoke vents, curtain boards and explosion relief covers the rest of Annex K, including curtain boards and explosion relief.

Annex N: suggested protection for specific industries

Annex N is titled suggested requirements of fire protection for specific industries. It is printed as informative and calls itself supplementary to Table 7G. Informative means advice. It tells you what the committee suggests and does not make a rule by itself, although a state or a fire officer may use it. It has four classes: low, ordinary, high A and high B. It says ordinary where Annex B says moderate. We read these as the same middle step, which is our reading.

Below 2,500 sq m of aggregate built-up area, one main table applies. Aggregate means all floors of the facility, whether process building, store, utility building or open storage. Our six-row summary follows (lpm is litres per minute).

Scope: NBC 2026 Annex N main table, read from the page images on 15 November 2026. The summary is ours and leaves out columns.

The pump figures come from notes 7a to 7d. Each asks for one electric main pump of at least the stated size and a standby of similar capacity. The last two want a diesel-engine standby and a jockey pump of at least 180 lpm. A jockey pump is a small pump that keeps the pipes under pressure. The sizes are 450 and 900 lpm at 50 m head, then 1,620 and 2,280 lpm at 70 m head. They are recommended minimums in an informative annex.

Some notes matter as much as the rows. Tiny licensed units need only extinguishers and buckets (note 4). A mixed complex is protected to its highest hazard (note 3). An industrial estate with many occupants is protected as ordinary hazard, with no high hazard unit in the building (note 5). Where water is not suitable, an alternative system is to be provided (note 11). And note 13 says the Annex B classes are only indicative, and that for designing hydrant and sprinkler systems the classification in IS 13039 and IS 15105 should be followed strictly.

Above 2,500 sq m: the appendices

Above 2,500 sq m, the main table gives no numbers of its own. It points you to four appendices that go trade by trade.

Appendices 1, 2 and 3 are lists of trades for low hazard, ordinary hazard and high hazard A, with 49, 61 and 32 entries. Appendix 4 is different. It is for high hazard B and lists plant areas, such as process units, tank farms and pump houses, not trades. Every appendix carries the same heading condition of more than 2,500 sq m aggregate built-up area. None of them uses the G1, G2 and G3 labels. They use the annex’s own class names.

So to find your trade, look it up in Annex B first, then look for it by name in the appendix of the matching class. Do not stop at the first match. The lists overlap and do not always agree with Annex B, as the next section shows. If your trade is missing or appears twice, take the printed row to your fire officer and ask which one applies.

• Rice mills: extinguishers, hose reels and hydrants required, sprinklers marked not required in process and storage blocks, and a manual alarm if the largest building exceeds 2,000 sq m.
• Plastic goods manufacturing: hydrants, hose reels and extinguishers required. Sprinklers in process blocks if the combined floor plate exceeds 2,000 sq m, and in raw material and finished goods storage. The row warns that many of the chemicals react with water and that a system not using water should then be used.

Special hazards, special systems

Water is not the right answer for every fire. A burning liquid or a metal powder can get worse with plain water, so the standard lists special systems. Table 11 marks which suppression systems suit which room or hazard. The plain-words description of each system is our own background, not the standard’s wording.

• Foam: a blanket over a burning liquid that cuts off its air. Table 11 marks a foam sprinkler system suitable for a paint and varnish store and for above-ground fuel oil storage. Note 1 says that where ignitable or water-miscible liquids are involved, a water spray should be supplemented with foam.
• Water spray: fixed nozzles that cool tanks and equipment. Marked suitable for a paint and varnish store and a generator room, and not suitable for a water-reactive chemical store.
• Dry powder: powder flooding that smothers the fire. Marked suitable for a water-reactive chemical store. Annex N asks for special dry powder systems in aluminium and magnesium powder plants.
• High-expansion foam: a very light foam that fills a large space. Annex N says it should be installed in aircraft hangars.

Note 2 under Table 11 says the chemical safety data sheet should be read to choose the right agent. Our guide to sprinkler versus fire suppression systems explains how these systems differ.

Where the annex and the tables do not match

The standard does not always agree with itself. We report these as printed and do not say which is right.

• Saw mills: Annex B puts them in G3, and Table 7G asks sprinklers in every high hazard row. The Annex N row for saw mills above 2,500 sq m marks sprinklers not required.
• Rice mills: Table 7G asks moderate units above 3,001 sq m for sprinklers. The Annex N rice mill row marks them not required. For a moderate unit of 501 to 2,000 sq m, Table 7G also asks for a wet riser and detection, which the Annex N row for 500 to under 1,500 sq m does not.
• Foamed plastics: Annex B puts foam plastics in G3. The Annex N ordinary hazard appendix lists foamed plastics, and the high hazard A appendix lists them as well.
• Substations and battery charging: Annex B puts electric substations in G2 and battery charging stations in G3. The Annex N low hazard appendix names both.
• Studios, distilleries and mattress making: Annex B puts cinema and TV studios, distilleries and mattress making in G2. The high hazard A appendix names all three. Linoleum factories and spray painting go the other way. Annex B puts them in G3 and the ordinary hazard appendix names them.
• Tanneries: Annex B puts them in G1. The low hazard appendix and the ordinary hazard appendix both list them, as printed. Annex N note 13 says Annex B is only a guide for ready reference, which is why the fire officer’s row decides.

A careful reading is that Table 7G sets the rows and Annex N is the suggestion that goes with it. That is our reading. If your unit sits on one of these seams, put the question to the fire officer. For the table rows, read our guide on factory and godown fire protection, and for exits and fire walls our guide on factory exits, fire walls and compartments.

Practical steps for an owner

• Get the class confirmed in writing by your fire officer, with the row that applies. Do not rely on a blog or a brochure.
• Count the whole area. The annex counts aggregate built-up area, all floors and buildings. Keep a current drawing and re-check after every shed you add.
• Follow the heaviest. If your complex has a plastics store, paint room or battery room, ask before you build it. Protection follows the highest hazard.
• Keep records of tank levels, pump runs and valve checks, with dates. This is practice. See fire safety maintenance for building owners.
• Special systems need specialist care. A foam, spray or powder system should be tested and serviced by a competent vendor on a written schedule. This is practice, not a clause.
• Keep stock and exits in order. See warehouse fire safety in India, warehouse and distribution centre fire risks and factory fire exits and blocked stairs. For one high hazard trade, see saw mill and timber yard fire safety. For one state’s rules, read Gujarat fire rules 2026 for industrial units. Our related cards cover firecracker factory blasts and Gujarat industrial estates.

Worked examples

These are illustrations of how to read the printed pages, not the legal answer for any real building. A real building is decided by its approved plan, your state rules and your fire officer.

A plastic-moulding unit. Annex B lists plastic goods manufacturing in G2. Say its sheds add up to 2,400 sq m. The Annex N ordinary hazard row for 1,500 to under 2,500 sq m suggests extinguishers, hose reels, wet riser, down comer, yard hydrant, manual alarm and automatic detection, but no sprinklers, with a 60,000 litre ground tank and a main pump of at least 1,620 lpm at 70 m head. Now add a shed to make 2,600 sq m. The unit leaves the main table and falls under the plastic goods appendix row, which asks for sprinklers in process blocks if the floor plate exceeds 2,000 sq m, and in stores. With cartons and packing inside, Table 7G note 1 would lift those areas to CL-6, which is our reading.

A rice mill. Annex B lists rice mills in G2. Say it has 1,200 sq m in all. The Annex N row for 500 to under 1,500 sq m suggests extinguishers, hose reels and a yard hydrant, a 40,000 litre ground tank and a main pump of at least 900 lpm at 50 m head. Table 7G is stricter for the same size and also asks for a wet riser and detection. So the owner has two printed answers for one mill, and that is a fair question for the fire officer.

What this means for you

• Factory and mill owners: find your trade in Annex B, write down your class and aggregate built-up area and ask your fire officer to confirm both.
• Building managers: check for a server room, battery room or generator room. These can be high hazard rooms.

Ask your fire officer

These are fair questions for a factory owner, an estate association or the fire office.

1. Which hazard class and which row of Table 7G, or of our state’s rules, covers this unit, and where is that written?
2. Where the national tables and the informative annex differ, which one does our state apply?
3. Do any rooms here, such as a server room, battery room, paint store or generator room, need extra protection?
4. Is water the right agent for what we store, and who services our pumps and any special system?

Where this stands in law

The National Building Construction Standards 2026, Part F, is voluntary. It binds a building only once a state or local authority adopts it, through its byelaws or its Fire Act. Until then your state’s building rules and the fire department decide what applies. Annex N is informative even in the standard itself. Factories also fall under labour, explosives and pollution laws that this chapter does not cover. Our guide to fire safety laws in India explains the layers. This guide is general safety information. It is not legal or engineering advice, and it does not tell you whether a particular building complies.

What we could not confirm

• Which class a particular trade falls in. We quote a few lines of a long list laid out in three columns.
• How the printed differences between Annex B, Table 7G and Annex N are meant to be read.
• How a state that has adopted the standard may have changed these rows.
• Any real unit’s class or row. That needs its approved drawings and a site visit.
• The listed videos. They were checked for public status and embedding and loaded in the YouTube player on a local test page, but were not watched in full.

Do this today

Find your trade in the hazard class list, or ask your architect to. Write down your class and your aggregate built-up area, and take both to your fire officer. Then read our maintenance guide for building owners and check when your pumps and tanks were last tested. Our chapter on factories, godowns and hazardous industries goes further.