In short. Generator fire and site safety rests on five things: diesel storage and spill containment, hot exhaust and its discharge, ventilation and battery gases, electrical isolation and earthing, and safe access for operation, refuelling and emergencies. In India the controlling references include the Petroleum Rules, the National Building Code, CEA regulations and CPCB stack height rules. Distances and approvals depend on the specific site and must be confirmed by competent personnel and the relevant authority.
Why location decides most of the risk
A diesel generator brings fuel, heat, rotating machinery and high fault energy into a building or yard. Whether that is safe depends far more on where and how the set is installed than on the set itself. A set placed in a basement next to the car park ramp, a set whose exhaust discharges beside a fresh-air intake, or a set that floods every monsoon is a hazard however well it is built. The review therefore covers the completed arrangement and the way the set will be fuelled, inspected and maintained over its life. A site survey, described in Generator Site Survey, is where this begins.
Fuel storage and spill control
Diesel is classified as a Class B petroleum product. Storage above the exemption limits in the Petroleum Rules requires a licence from PESO, and the quantity limits, tank construction and separation distances should be confirmed for each site rather than assumed. Below those limits, good practice still applies.
- Bund or double-wall the tank so that a leak is contained; a bund holding at least 110 percent of the largest tank is a widely used rule.
- Keep fuel out of floor drains and storm-water channels, so a spill cannot reach a nala or the municipal drain.
- Route fuel lines where they cannot be crushed, and support flexible connections near the engine against vibration.
- Provide a fill point that a tanker can reach without dragging hose through occupied areas.
- Inspect water separators and drain them, particularly before and after the monsoon.
Fuel system design is covered in Generator Fuel Systems.
Exhaust, stack height and hot surfaces
Exhaust gas leaves a loaded diesel engine at several hundred degrees Celsius. Pipework must be lagged or guarded where people can reach it, kept clear of combustible materials, and fitted with a flexible section to isolate engine movement. The discharge must be away from windows, air intakes and neighbouring buildings. For diesel gensets, CPCB sets a minimum stack height.
H = h + 0.2 × √kVA
Here H is the minimum stack height in metres above ground, h is the height of the building in metres where the set is installed, and kVA is the generator rating.
(illustrative) A 500 kVA set beside a 15 metre building needs a stack of at least 15 + 0.2 × √500, which is about 15 + 4.5, or 19.5 metres. A taller stack adds backpressure, so the exhaust size must then be checked against the engine maker’s limit, as explained in Generator Exhaust Systems.
Ventilation, batteries and electrical safety
Ventilation
A generator room must remove engine and alternator heat and supply combustion air. Inadequate airflow raises room temperature, derates the set and causes high-temperature shutdowns on summer afternoons. Hot radiator air must not recirculate to the intake. See Generator-Room Ventilation.
Batteries
Lead-acid starting batteries can release hydrogen while charging. Keep them ventilated, away from sparks, secured, and with terminals covered. Battery energy storage systems introduce a different set of hazards and need specialist review.
Electrical isolation and earthing
Provide a lockable means of isolation for the set and the changeover, clear labelling of every source, a permanent earthing arrangement tested and recorded, and an emergency stop reachable without passing the running engine. A set that can start automatically on mains failure must carry a warning to that effect.
Access, fire fighting and site review checklist
Technicians need room to service the set, change filters, remove a radiator or replace a battery; fire fighters need a clear approach and to know where to isolate fuel and power. Suitable portable extinguishers, typically carbon dioxide or dry chemical powder rated for oil and electrical fires, should be placed near the exit.
| Area | Check | Typical reference |
|---|---|---|
| Fuel quantity | Is storage within exemption limits, or is a licence needed? | Petroleum Rules, PESO |
| Spill containment | Bund or double-wall tank, no drain path | Good practice, local pollution rules |
| Exhaust | Stack height, discharge location, lagging | CPCB genset rules |
| Ventilation | Airflow sized for heat rejection and combustion | Manufacturer data |
| Electrical | Isolation, interlocks, earthing, labels | CEA regulations, IS 3043 |
| Fire | Extinguishers, escape route, separation from occupied areas | National Building Code, local fire authority |
| Flooding | Plinth above known flood level, cable entries sealed | Site history |
Any unresolved item should remain recorded as open until it is closed, rather than disappearing at handover. Our position on documentation is set out in Document & Evidence Status.
Related photographs and videos
Common mistakes
- Placing a set in a basement because it is the only free space, without planning ventilation and exhaust, which leads to overheating and fumes in occupied areas.
- Storing extra diesel in drums beside the set, which adds an uncontrolled fire load and can exceed licensing limits.
- Running the exhaust out at ground level beside a walkway, which exposes people to hot gas and fails the stack height rule.
- Installing the set at ground level in a low-lying yard, which floods during heavy monsoon rain and damages the alternator and controls.
What to send us
Send a site layout or sketch showing the proposed set location, building heights, nearby openings and air intakes, the fuel quantity you intend to store, and photos of the location and access route. Mention any flooding history and the fire authority’s requirements if known. Use the application engineering enquiry and we will review the installation constraints.
Questions engineers ask
Do I need a PESO licence for my generator’s diesel tank?
It depends on the quantity and how it is stored. The Petroleum Rules set exemption limits for Class B products such as diesel; above them a licence is required. Confirm the current limit and conditions with PESO for your installation.
How is the minimum exhaust stack height calculated?
CPCB requires H = h + 0.2 × √kVA, where h is the building height in metres. The stack must also be checked for engine backpressure, which rises with length and bends.
Can a generator be installed on a building terrace?
Often yes, provided the structure is assessed for the weight and vibration, fuel storage and refuelling are planned, and the exhaust and noise meet the rules. Access for lifting during installation and overhaul also needs planning.
What fire extinguishers should be kept near a DG set?
Carbon dioxide and dry chemical powder extinguishers suitable for oil and electrical fires are typical, with the type and number confirmed against the National Building Code and the local fire authority.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and Service Engineer, Reddy Generators. Last updated 19 October 2026.