Explosion-Proof Phones in Pharmaceutical Plants: Solvent Zones, Powder Zones and GMP Camera Policy

A refinery is obviously a classified site — nobody argues about it. A tablet plant looks clean, air-conditioned and orderly, and yet the granulation suite inside it routinely carries a more demanding explosion risk than the diesel yard outside, because the hazard in that room is not vapour. It is powder.

This page sets out where the classified zones sit in an API plant and in a formulation plant, why fine organic powders ignite so easily, what marking a handheld needs to enter each area, and — for Indian sites — what the law does and does not require. Much of what is published about the Indian position is wrong, so the scope limits are stated here in full.

Where are the hazardous areas in a pharmaceutical plant?

There are two different industries inside pharmaceutical manufacturing, and they carry two different hazards.

API and bulk drug: a flammable-vapour site

API synthesis is organic chemistry at scale. Reactors, distillation columns, solvent recovery, centrifuges, filtration and dryers all hold large inventories of flammable liquid — ethanol, isopropyl alcohol, methanol, acetone, ethyl acetate and toluene above all. Acetonitrile puts the same hazard into the QC laboratory, the area most often left out of a classification review.

The pattern will be familiar to anyone from petrochemicals: vessel and tank interiors are Zone 0, the vicinity of open charging points, sampling points and centrifuge discharge is Zone 1, the wider bunded area is Zone 2. Drying and milling then lay dust zones on top, because a solvent-wet cake becomes a dry powder somewhere inside the dryer. One correction, since it appears wrongly on many supplier pages: dichloromethane is not a flammable solvent under normal handling conditions. It is a toxicity and containment hazard, and belongs on a different risk register.

Formulations: predominantly a combustible-dust site

Oral solid dosage manufacturing barely uses solvent by comparison and is therefore often assumed to be non-hazardous. It is not. Dispensing, sifting, milling, granulation, blending, compression and coating all generate airborne clouds of fine organic powder, so these are dust-classified areas — Zone 20, 21 and 22 rather than Zone 0, 1 and 2. The case that catches people out is film coating: aqueous coating is a dust problem only, while organic solvent-based coating puts a flammable vapour source and a combustible dust source in the same room at the same time.

Treat that as a pattern, not an answer. The zones that apply to your site come from your own hazardous area classification drawing, for your own materials, quantities and ventilation. Any supplier who calls a device “approved for your granulation area” without having seen that drawing is guessing.

Why does a fine pharmaceutical powder explode at all?

Because the ignition energy required is far lower than most people assume, and pharmaceutical processing is engineered to lower it further.

Every dust has a minimum ignition energy (MIE) — the smallest spark energy that will ignite a cloud of it in air. Many pharmaceutical powders, including excipients such as lactose, microcrystalline cellulose, starch, mannitol and magnesium stearate, have MIE values low enough to be reached by an electrostatic discharge from a human body, on the order of a few tens of millijoules. That is why a formulation plant insists on conductive footwear, earthed transfer containers and antistatic garments — and why an uncertified plastic-cased smartphone is a real hazard in a granulation suite despite having no visible spark source: the risk is stored charge and an unprotected battery circuit, not a flame. Milling and micronisation make it worse on purpose — finer particles mean a lower MIE and a more violent explosion.

Two further mechanisms change what equipment you can use:

• The layer hazard. Dust does not only burn as a cloud. A settled layer on a warm surface insulates it, smoulders and self-heats. This is why dust-rated equipment is marked with a maximum surface temperature in degrees Celsius — T135°C, for example — rather than the T1 to T6 class used for gas, and why ingress protection is part of the protection concept: dust must be kept out of the enclosure, not merely away from sparks.
• Secondary explosions. A small primary event inside a mill or duct lifts dust settled on beams, ledges and cable trays, which then ignites. That is what turns a contained incident into the loss of a building, and why housekeeping in a tablet plant is a safety control rather than a cosmetic one.

What marking does a phone need to enter a granulation suite?

It needs a dust marking. A gas-only certificate — what most industrial “explosion-proof” phones carry — does not permit entry to a Zone 21 or Zone 22 area at all. A device crossing from the solvent block to the formulation block must carry both a G (gas) and a D (dust) line, in this form:

• II 2G Ex ib IIC T5 Gb
• II 2D Ex ib IIIC T135°C Db, with an ingress rating such as IP68

Read line by line:

• 2G / Gb — permitted in Zone 1 and Zone 2 gas areas. Not Zone 0.
• 2D / Db — permitted in Zone 21 and Zone 22 dust areas. Not Zone 20.
• IIC — the most demanding gas group, covering hydrogen and acetylene, and so covering every solvent an API plant handles.
• IIIC — the conductive dust group, the most demanding of the three.
• T5 — gas temperature class; maximum surface temperature 100°C.
• T135°C — maximum surface temperature for the dust case, to be compared against your own powder’s cloud and layer ignition temperatures.
• ib — intrinsic safety, equipment protection level ib.

Plainly: a device marked that way can be carried into the granulation suite, the coating room, the compression hall, the tank farm and the reactor block — and cannot go inside a vessel, a mill chamber, a fluid-bed bowl or a bag-filter housing. Where a datasheet and the certificate disagree on maximum surface temperature, the certificate governs; ask for the certificate covering the exact model and revision you are buying. Infinity’s Zone 1 and Zone 21 rated handhelds — the EX72 Plus, EX027, EX101 Ultra and the WT01 wearable — ship with that documentation package rather than with a badge.

What does Indian law actually require for a handheld device?

PESO approval is scoped, not universal

PESO — the Petroleum and Explosives Safety Organisation, headed by the Chief Controller of Explosives — is the recognised Indian authority for approving electrical apparatus used in hazardous areas, and buyers, EPC contractors and inspectorates routinely ask for its letter. But the scope stated in PESO’s own approval procedure is apparatus used in hazardous areas of premises licensed under the Petroleum Rules 2002, the Gas Cylinders Rules 2016 and the SMPV(U) Rules 2016. A pharmaceutical plant holding no such licence is not automatically inside PESO’s approval remit. That does not make the approval irrelevant — a solvent tank farm above threshold quantities may bring a licence with it, and procurement asks for the letter regardless — but “PESO approval is legally mandatory for every electrical device in every Indian factory” is not a correct statement of the law.

PESO’s Ex scheme covers gas, not dust

That published procedure makes no reference to dust atmospheres at all — no IS/IEC 60079-31, no 60079-10-2. Dust is not covered by the scheme. For a formulations plant, where the entire hazard is powder, this matters: a PESO approval letter on its own tells you nothing about whether a device is fit for a Zone 21 room. Ask for the dust certification separately and read the D line of the marking yourself.

Dust is covered elsewhere — but for the fixed installation

The Central Electricity Authority (Measures relating to Safety and Electric Supply) Regulations 2023 address dust directly. Regulation 39(iv) requires electrical installations in premises where inflammable material is handled to be “flame proof, dust tight, totally enclosed or any other suitable type” depending upon the hazardous zones involved. Check the scope before anyone quotes it at you in a tender: regulation 39 applies where electricity above 250 V is used. It binds the plant’s fixed electrical installation. It does not, on its own terms, reach a battery-powered handheld, and a supplier claiming that this regulation requires an Ex-certified phone is over-reading it.

The real legal hook for a handheld is the Factories Act

Section 37(1)(c) of the Factories Act 1948 is the provision that applies. Where a manufacturing process produces dust, gas, fume or vapour likely to explode on ignition, all practicable measures shall be taken to prevent an explosion — including the “exclusion or effective enclosure of all possible sources of ignition.” Two things follow. The duty expressly covers dust as well as gas, so a tablet plant sits squarely inside it. And it is functional rather than prescriptive: no Indian rule names mobile phones, because none needs to. If an uncertified handset in a classified area is a possible source of ignition, excluding or enclosing it is what the section asks of the occupier. Specifying a certified device discharges that duty; so does a prohibition that is written, enforced and auditable.

Check which standard your tender cites

IS 5571, the selection standard still appearing in a striking number of Indian tender documents, has been withdrawn and superseded by IS 16724:2018, India’s adoption of IEC 60079-14. A specification citing IS 5571 is citing a dead standard. IS 5572:2009 remains current for area classification — but it covers gases and vapours only, so a formulation plant cannot be classified under it alone.

How does a foreign-certified device get accepted in India?

Through IECEx, in practice. PESO accepts an IECEx Certificate of Conformity together with the Quality Assessment Report and the test report as the documentary basis for an application. The EU’s ATEX route is restricted to manufacturers with EU manufacturing locations, which rules it out for most non-European manufacturers, so IECEx is the general-purpose route into India. Infinity supplies that full certification and test documentation package, which is what supports a PESO submission — ask any supplier, us included, for the documents rather than for a badge.

Does GMP ban cameras and mobile phones in manufacturing areas?

No. This is the most persistent myth in the industry, and the regulatory texts say close to the opposite.

India’s revised Schedule M, notified as G.S.R. 922(E) on 28 December 2023, contains no mention of cameras, mobile phones, hazardous areas, audit trails or ALCOA anywhere in its text. What it does contain, at clause 20.4, is a requirement to keep a record of any data change made, the previous entry, the person who made the change and when — which is functionally an audit trail, and should be described that way. The widely repeated claim that Schedule M “mandates audit trails” is not what the document says. Clause 7.7 bans wristwatches, cosmetics and jewellery in clean areas; mobile phones are not in that list.

The only regulator anywhere that names mobile phones is EU GMP Annex 1 (2022) — and it permits them. Clause 7.9 states that electronic devices used in cleanrooms, such as mobile phones and tablets, supplied by the manufacturer solely for use in the cleanrooms, may be acceptable if suitably designed to permit cleaning and disinfection commensurate with the grade in which they are used. Clause 4.17 goes further and encourages remote cameras for observing grade A and grade B operations.

The regulatory concern about a device in a cleanroom is therefore contamination control — whether it can be cleaned and disinfected to the grade of the room. It is not ignition, and it is not confidentiality. Where a plant nonetheless bans phones on the shop floor, that is site SOP driven by intellectual-property policy, security and contamination control: a legitimate choice, but a company rule rather than a regulatory requirement. The practical alternative to a controlled, cleanable, certified, centrally managed device is not a phone-free plant. It is everyone’s uncertified personal handset in a pocket, ungoverned.

Which Indian clusters does this affect most?

• The Hyderabad belt — Jeedimetla, Bollaram, Patancheru, Genome Valley — the densest and most solvent-heavy API concentration in India. Gas zones dominate, with dust zones around drying and milling.
• Gujarat — Ankleshwar, Vapi, Vadodara, Dahej — the other great API and intermediates corridor, same vapour-led profile.
• Visakhapatnam and its API parks: greenfield, export-oriented, largely solvent chemistry.
• Baddi (Himachal Pradesh) and Sikkim: formulations territory — powder handling, very little solvent, an almost purely Zone 21 and 22 problem.
• Pune, Chhatrapati Sambhajinagar (Aurangabad) and Goa: mixed, formulations and injectables predominating.

Most large Indian groups run both kinds of site, which is why one dual-certified device specification is easier to manage than separate gas-only and dust-only fleets.

What should you check before you buy?

• Your own classification drawing — zone, gas group, dust group, and the ignition temperatures of your own powders.
• That the certificate carries both a G and a D marking if the device will cross between blocks, and that Gb/Db match your zones.
• Declared maximum surface temperature against your powder’s layer and cloud ignition temperatures, not a generic table.
• Ingress rating — for dust entering the enclosure, and for surviving your cleaning and disinfection regime.
• Whether camera capture can be disabled or governed by mobile device management profile, with a logged procedure for re-enabling it.
• The certificate for the exact model and revision ordered, plus the documentation package supporting a PESO submission where your site requires one.

Send us the area classification summary for the block in question and we will tell you which zones our devices cover and, just as importantly, which they do not.

Frequently asked questions

Is a granulation suite a hazardous area?

Usually yes — a dust-classified one. Granulation, milling, sifting, blending and compression all generate clouds of fine organic powder, so these rooms are typically Zone 21 or Zone 22, with Zone 20 inside the equipment itself. The exact zones come from your site’s own classification study, but a formulation suite treated as non-hazardous has probably never been assessed.

Does PESO approval cover dust zones?

No. PESO’s published Ex approval procedure addresses gas and vapour atmospheres; it makes no reference to dust, to IS/IEC 60079-31 or to dust area classification. A PESO letter therefore tells you nothing about whether a device is fit for Zone 21 or Zone 22. For a powder-handling plant, ask for the dust certification separately.

Do Indian regulations require an explosion-proof mobile phone in a pharmaceutical plant?

No Indian rule names mobile phones. The applicable duty is section 37(1)(c) of the Factories Act 1948: where a process produces dust, gas, fume or vapour likely to explode on ignition, all practicable measures shall be taken, including the exclusion or effective enclosure of all possible sources of ignition. A certified device is one way to discharge that duty; an enforced prohibition is another.

Does GMP prohibit cameras in a pharmaceutical cleanroom?

No. EU GMP Annex 1 (2022) clause 7.9 expressly permits mobile phones and tablets supplied for cleanroom use where they are designed to permit cleaning and disinfection appropriate to the grade of the room, and clause 4.17 encourages remote cameras for observing grade A and B operations. India’s revised Schedule M does not mention cameras or phones at all. Shop-floor phone bans are site policy, not GMP.

Is IS 5571 still a valid standard to cite?

No — IS 5571 has been withdrawn and superseded by IS 16724:2018, India’s adoption of IEC 60079-14. Many Indian tender documents still cite the withdrawn number, so it is worth correcting a specification before it goes to bidders. IS 5572:2009 remains current for area classification, but covers gases and vapours only and does not classify dust areas.

Can one phone be used in both the solvent block and the tablet plant?

Yes, provided it is certified for both. A device marked II 2G Ex ib IIC T5 Gb and II 2D Ex ib IIIC T135°C Db covers Zone 1 and 2 gas areas and Zone 21 and 22 dust areas, spanning the reactor block, tank farm, granulation suite and compression hall. It does not cover Zone 0 or Zone 20.