Rules 24-25 explained: this guide covers what it means, who it applies to, the step-by-step process, documents required, fees, due dates and penalties in India — so you can stay compliant with confidence and avoid costly mistakes.
Rule 24 covers how a factory handles dust, noxious gas, fumes and other impurities: exhaust systems must be separate and treated, and nobody may enter a workplace or confined space until the air is within permissible limits. Rule 25 applies where a factory artificially increases humidity and sets out heat-stress risk assessment, work-rest cycles, drinking water, supervision, training, humidity tests and instruments.
Rule 24 has three duties: keep flammable-fume exhausts separate from other ventilation and from combustion flues; neutralise, sterilise or deodorise harmful discharges; and keep people out of workplaces and confined spaces until levels are within permissible limits. Rule 25 applies where humidity is artificially increased and has eight duties, including risk assessment, a work-rest cycle, drinking water with electrolytes where appropriate, trained staff and recorded humidity tests.
The Code basis
Section 23(2) of the Occupational Safety, Health and Working Conditions Code, 2020 (the OSH Code) lists matters the Central Government may prescribe, including an environment without dust, noxious gas, fumes and other impurities, and adequate standards of humidification, ventilation and cooling of the air in workrooms. Rules 24 and 25 do this for factories. Read them with rules 22 and 23; see our article on rules 22 and 23 and our section 23 explainer.
These are Central Rules; where the State Government is the appropriate Government, the State's own rules apply. If your plant handles solvents, dusts or hot, humid processes and you want a written control plan aligned with these rules, our labour law compliance team can help.
Rule 24: precautions against dust, noxious gas, fumes and other impurities
The employer of every factory shall ensure that:
| Clause | Duty |
|---|---|
| (i) | Exhaust systems for removal of flammable fumes, gases, mists, vapours or residues, wherever required, are not connected to any other ventilating system and are not discharged into a chimney or flue used for conveying gases of combustion |
| (ii) | Where fumes, gases, mists, vapours, dust or refuse discharged from exhaust systems are likely to harm health or be noxious to employees or the neighbourhood, exhaustion is through a system that neutralises toxic substances, sterilises infectious substances and deodorises fumes, gases, mists or vapours |
| (iii) | No employee is required or allowed to enter any workplace or confined space until practicable measures have brought levels of noxious gas, fume, vapour or dust within the permissible limits |
Clause (i) is a fire and explosion control. A flammable-fume exhaust that is tied into general ventilation or a combustion flue can carry the hazard elsewhere. Keep it independent.
Clause (ii) covers the neighbourhood as well as employees. It does not prescribe technology: it names the outcome (neutralise, sterilise, deodorise) and leaves the choice of scrubber, filter or other system to the employer, subject to its effectiveness.
Clause (iii) turns on two phrases: "required or allowed" and "permissible limits". The employer cannot defend an entry on the basis that the employee volunteered. The rule does not list the limits; they are set elsewhere. The Code's Second Schedule includes matters for occupational safety and health standards, and section 88 of the Code deals with permissible exposure limits; see our Second Schedule explainer and our sections 86 to 88 explainer. Confined-space entry needs measurement before entry, not only a general instruction.
Rule 25: artificial humidification
Rule 25 applies to a factory "in which humidity of the air is artificially increased" and requires the employer to ensure:
| Clause | Duty |
|---|---|
| (i) | If employees are exposed in any tasks to extreme heat and high humidity and the hazard cannot be eliminated, risks to safety and health are assessed and controls to reduce them are put in place |
| (ii) | The risk assessment takes into account appropriate protective clothing against hazardous substances that can raise heat stress, and the fact that respiratory protectors are uncomfortable and less likely to be used in extremely hot environments |
| (iii) | Where part of the risk arises from metabolic heat or direct sunlight and high outdoor air temperature, and other methods are impracticable, a work-rest cycle, preferably in a shaded, air-conditioned or cooler space, is provided |
| (iv) | Sufficient drinking water, with proper electrolytes where appropriate, at easily accessible places |
| (v) | Where residual heat-stress risk remains, employees are adequately supervised so they can be withdrawn if symptoms occur; first-aid facilities and trained staff are available |
| (vi) | Employees in extreme hot and humid conditions are instructed and trained (a) to recognise heat-stress symptoms in themselves or others and the steps to prevent onset and emergencies, and (b) on action when accident risk increases due to high temperature or humidity |
| (vii) | Tests for relative humidity are carried out and recorded; if the level is harmful, it is artificially regulated so that humidification and temperature do not cause discomfort; the water used comes from public supply or another drinking water source, or is purified before use |
| (viii) | Instruments for measuring and recording humidity and temperature are provided and maintained at appropriate locations |
The order of controls matters. Clause (i) starts with a hazard that "cannot be eliminated", then assesses and controls it. Clause (iii)'s work-rest cycle applies "when other methods of eliminating the risk are impracticable". The rule thus asks the employer to try to engineer out the hazard first and to rely on rest cycles and supervision for the remainder.
Protective equipment cuts both ways. Clause (ii) recognises that protective clothing and respirators can add to heat stress or be left unused in extreme heat. A risk assessment that says "issue respirators" without looking at heat does not meet it.
Water and records. Clause (vii) has two elements: the humidity tests are recorded, and the water used in humidifiers is of drinking quality or purified. Clause (viii) requires instruments to be provided and maintained at appropriate locations; a hygrometer that is broken or kept in the office does not do this.
Where the two rules touch other provisions
- Heat-stress first aid connects to rule 54 on first aid and medical appliances; see the later article in this cluster.
- Section 6(2)(c) of the Code requires information, instruction, training and supervision as necessary for employees' health and safety; rule 25(v)-(vi) is a concrete case. See our section 6 explainer.
- Notifiable diseases such as silicosis or poisonings that can follow dust and fume exposure trigger the notice under rule 8; see our rule 8 explainer.
Consequences
Rules 24 and 25 state no penalty of their own. Contravention is handled under the Code's penalty provisions; see our section 94 explainer.
Practical examples
Example 1. A paint-mixing unit has a solvent-vapour exhaust. During an audit the exhaust duct is found tied into the general ventilation trunk. Under rule 24(i) the employer separates it, adds a treatment stage under clause (ii), and introduces a pre-entry gas test for the storage tank under clause (iii).
Example 2. A cotton spinning mill uses humidifiers. The employer records humidity readings at fixed stations, fits working thermometers and hygrometers, arranges cooler rest areas, stocks electrolyte drinks and trains supervisors to recognise heat-stress symptoms. The humidifier water is taken from the drinking-water line.
Need help with factory air-quality and heat-stress compliance?
Exhaust design, confined-space entry and heat-stress controls need records that an inspector can follow. Our labour law compliance team can help you turn rules 24 and 25 into checklists, training records and measurement logs.
Key takeaways
- Flammable-fume exhausts must be separate from other ventilation and from combustion flues.
- Harmful discharges must be neutralised, sterilised or deodorised before release.
- No one may be required or allowed to enter a workplace or confined space until levels are within permissible limits.
- Rule 25 applies where humidity is artificially increased, and starts with risk assessment.
- Work-rest cycles, electrolyte drinking water, supervision, first aid and training follow for residual heat-stress risk.
- Humidity tests must be recorded and instruments maintained; State rules apply where the State is the appropriate Government.
Read next
- Rules 22 and 23: factory cleanliness, ventilation, temperature and humidity
- Rules 26 to 29: mines cleanliness, ventilation, dust and humidification
- Section 23 of the OSH Code: employer responsibility
- Health provisions in factories: cleanliness, ventilation, lighting
Disclaimer: Based on the Occupational Safety, Health and Working Conditions Code, 2020 (as enacted) and, where noted, the Occupational Safety, Health and Working Conditions (Central) Rules, 2026 (G.S.R. 345(E), 8 May 2026), as on 30 September 2026. The Code is in force from 21 November 2025; some provisions may be notified later, and State Governments make their own rules for establishments where the State is the appropriate Government. Verify the current position before acting.