Laboratory safety and good laboratory practice

In short

Laboratory safety is the set of engineering controls, work practices, protective equipment and legal duties that prevent chemical, fire, electrical and biological harm in a laboratory; good laboratory practice (GLP) is the quality system that makes the data produced there traceable, reproducible and defensible. The two are inseparable in analytical chemistry: an uncalibrated balance, an unlabelled reagent and an unvented fume hood are simultaneously a safety failure and a data failure. Indian testing laboratories work to ISO/IEC 17025:2017 under NABL accreditation, pharmaceutical labs to Schedule M of the Drugs and Cosmetics Rules (revised 2023; the extended deadline for small manufacturers ended 31 December 2025), and non-clinical safety studies to OECD GLP Principles monitored by the National GLP Compliance Monitoring Authority (NGCMA) under the DST. This topic is examined in B.Sc practical vivas, M.Sc entrance and CSIR-NET/GATE-CY general questions, and is asked in virtually every QC/QA interview — at Dr Reddy's, Sun Pharma, Cipla, Hindustan Unilever, Tata Chemicals, SGS, Eurofins, TÜV and the public labs (CSIR, FSSAI, state drug testing labs).

Explained

Hazard identification: GHS, labels and safety data sheets

• GHS (Globally Harmonised System) classifies chemicals by physical hazard (flammable, oxidising, explosive, gas under pressure, corrosive to metals), health hazard (acute toxicity, corrosion, sensitisation, carcinogenicity, mutagenicity, reproductive toxicity, STOT, aspiration) and environmental hazard.
• Nine pictograms: flame, flame over circle (oxidiser), exploding bomb, gas cylinder, corrosion, skull and crossbones (acute toxicity), exclamation mark (irritant/harmful), health hazard (the "chest" symbol for CMR/STOT), environment (dead fish and tree).
• A GHS label carries: product identifier, pictogram(s), signal word ("Danger" for the severer category, "Warning" for the milder), H-statements (hazard, e.g. H314 causes severe skin burns) and P-statements (precautionary), plus supplier details.
• Safety Data Sheet (SDS) — the modern name for MSDS — has 16 fixed sections; the ones used daily are 2 (hazards), 4 (first aid), 5 (firefighting), 7 (handling and storage), 8 (exposure controls, PPE, TLV/PEL), 9 (physical data: flash point, boiling point, vapour pressure), 10 (stability and incompatibility), 11 (toxicology: LD50/LC50) and 13 (disposal).
• NFPA 704 diamond: blue = health, red = flammability, yellow = reactivity/instability, white = special (OX oxidiser, W reacts with water, SA simple asphyxiant); each rated 0 (minimal) to 4 (severe). A common exam question: concentrated HNO₃ carries OX and a high health rating.
• Key toxicity and fire terms: LD50 (dose killing 50% of a test population, mg/kg body weight — lower means more toxic), LC50 (airborne concentration, ppm or mg/m³), TLV-TWA (8-h time-weighted average), TLV-STEL (15-min short-term limit), TLV-C (ceiling, never to be exceeded), IDLH, flash point (lowest temperature at which vapour forms an ignitable mixture), autoignition temperature, LEL/UEL (flammability limits in air %v/v).

Engineering controls, PPE and laboratory layout

• Hierarchy of controls (always answer in this order): elimination → substitution (e.g. replace benzene with toluene, CCl₄ with cyclohexane) → engineering controls (fume hood, local exhaust, interlocks, blast shield) → administrative controls (SOPs, training, restricted access, work permits) → PPE last, because it protects only the wearer and only if worn correctly.
• Fume hood: face velocity typically 0.4–0.6 m/s (0.5 m/s is the usual design target; the exact value depends on the hood type and the applicable standard). Work at least 15 cm inside the sash, keep the sash low, never store bottles inside, never use it as a disposal route for volatiles, and verify airflow before starting.
• Mandatory facilities: eyewash and emergency shower reachable within about 10 s of travel and tested regularly, fire extinguishers and fire blanket, first-aid box, sand bucket, spill kit, exhaust ventilation, non-slip floor, two means of exit, and a clearly marked emergency assembly point.
• PPE: side-shield safety spectacles or chemical splash goggles (a face shield when splashing or implosion is possible); cotton or flame-resistant lab coat, fully buttoned (synthetics melt onto skin); closed shoes — no sandals; gloves chosen by chemical, not habit — nitrile for general solvents and acids, butyl/Viton for chlorinated and aggressive solvents, neoprene for many acids and oils, latex only for aqueous/biological work (poor against solvents, and a sensitiser); cryogenic gloves and tongs for liquid N₂; respirators only after fit-testing.
• Glove breakthrough time matters more than thickness: thin nitrile fails quickly against acetone, DMF and chloroform. Remove gloves before touching door handles, keyboards, phones and notebooks.
• Housekeeping: no eating, drinking, chewing or cosmetics; no mouth pipetting (use a bulb or pipette aid); long hair tied; no lone working with hazardous operations; bench kept clear; aisles and electrical panels unobstructed.

Safe handling, storage and segregation of chemicals

• Dilution rule: always add acid to water slowly with stirring (the mnemonic "A to W"); never water to concentrated H₂SO₄ — the heat of dilution can boil and spatter the acid. Cool in an ice bath for large dilutions.
• Carry bottles in a carrier or bucket, never by the neck; transport cylinders strapped on a trolley with the valve cap on; secure cylinders upright by chain or clamp; acetylene cylinders always upright.
• Segregate by compatibility, not alphabetically. Classic incompatible pairs asked in exams:
  • Oxidisers (HNO₃, KMnO₄, perchlorates, peroxides, chlorates) away from organics, solvents and reducing agents.
  • Acids away from bases, cyanides (→ HCN), sulphides (→ H₂S), carbides and active metals.
  • Water-reactives (Na, K, LiAlH₄, CaC₂, SOCl₂, acid chlorides, alkali metals) stored dry, under kerosene/mineral oil where applicable, away from any aqueous work and from water-type extinguishers.
  • Picric acid, perchloric acid, ethers and di-isopropyl ether: peroxide and shock hazards — date on receipt and on opening, test old ethers for peroxides, never evaporate an ether to dryness, never distil a peroxide-former down to residue.
• Flammable storage: flammable-solvent cabinets, bonding and earthing while transferring, flame-proof refrigerators only (a domestic fridge's internal thermostat spark has caused laboratory explosions), quantity on the bench limited to the day's need.
• Cold-chain and light-sensitive reagents: amber bottles, desiccators for hygroscopics, labelled with name, concentration, preparation date, expiry/retest date and the preparer's initials. An unlabelled container is treated as hazardous waste — never sniffed or tasted to identify it.
• Specific high-risk reagents: HF (causes deep, delayed burns and hypocalcaemia — calcium gluconate gel must be stocked), bromine and mercury (vapour hazard; mercury spill kit, sulphur powder), perchloric acid (dedicated water-washdown hood), hydrazine, cyanides, chromic acid, and carcinogens such as benzidine and benzene (substitute wherever possible).

Fire, electrical and emergency response

• Fire classes (Indian practice, IS classification): A ordinary combustibles; B flammable liquids; C flammable gases; D combustible metals (Na, K, Mg, Al powder); E/electrical energised equipment; F/K cooking oils.
• Matching the extinguisher is the examined point: water (or foam) for A — CO₂ is ineffective on deep-seated class A fires, CO₂, dry chemical or foam for B, CO₂ or dry powder for electrical, special dry powder (graphite, sand, ternary eutectic chloride) for class D — never water or CO₂, and never water on a solvent fire (it spreads it) or on energised equipment.
• PASS operation: Pull the pin, Aim at the base, Squeeze the lever, Sweep side to side. Fight only a small, incipient fire with your back to an exit; otherwise raise the alarm and evacuate.
• Clothing fire: stop, drop and roll, or use the fire blanket/shower — never run.
• First aid basics: chemical in the eye — irrigate with the eyewash for at least 15 minutes, eyelids held open, then to a doctor with the SDS; skin contact — remove contaminated clothing and flush 15 min; acid or alkali burns are not neutralised on skin; inhalation — move to fresh air; ingestion — do not induce vomiting for corrosives or hydrocarbons; cuts from glass — control bleeding, check for embedded glass.
• Spills: evacuate if toxic or large, stop the source, ventilate, and contain from the outside inwards — inert absorbent or vermiculite for solvents, sodium bicarbonate or a commercial neutraliser for acids, citric acid or boric acid for alkalis, sulphur or a commercial amalgamating kit for mercury; collect into a labelled waste container; report every spill, however small.
• Electrical: earthed three-pin plugs, no daisy-chained extensions, ELCB/RCCB protection, dry hands, muffle furnaces and hot plates on non-combustible surfaces, and isolation before any maintenance. Glassware safety: never heat a closed system, inspect for star cracks, tape or shield vacuum desiccators, use a safety shield for pressure work, and discard chipped glass in a dedicated sharps/glass bin, not the dustbin.

Waste management and legal framework in India

• Segregate at source into halogenated solvents, non-halogenated solvents, aqueous acidic/alkaline, heavy-metal (Cr, Pb, Cd, Hg, As) solutions, cyanide waste (kept alkaline — never acidified), oxidisers, solid chemical waste and broken glass; each container labelled with contents and the date of first filling.
• Never pour solvents, mercury, heavy metals or concentrated acids down the sink; dilute, neutralise and discharge only where the SOP and the consent conditions permit. Treated effluent must meet the State Pollution Control Board consent limits under the Water (Prevention and Control of Pollution) Act, 1974 and the Air Act, 1981, administered through the Environment (Protection) Act, 1986.
• Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016 (as amended) govern storage limits, manifests (Form 10 transport documents), and disposal only through authorised CHWTSDF operators and registered recyclers; a hazardous-waste authorisation from the SPCB is required. Bio-Medical Waste Management Rules, 2016 (colour-coded yellow/red/white/blue bags) apply to clinical and microbiology laboratories.
• Occupational safety law: the four Labour Codes are in force from 21 November 2025; the Occupational Safety, Health and Working Conditions Code, 2020 has replaced the Factories Act, 1948 and the BOCW Act, and carries forward the duties on hazardous processes, safety committees, occupational health examinations, notification of dangerous occurrences and maintenance of records in a works-type laboratory. State rules framed under the Code supply the detailed numbers, so quote the Code and the relevant state rule rather than the old Factories Act sections.
• Other statutes commonly cited: Manufacture, Storage and Import of Hazardous Chemical Rules, 1989 (MSIHC, threshold quantities and on-site emergency plans), the Petroleum Act/Rules and Gas Cylinders Rules, 2016 (PESO licensing for solvents and cylinders), the Atomic Energy (Radiation Protection) Rules, 2004 with AERB licensing for radiation sources, the Poisons Act and state poison rules, NDPS Act controls on narcotic standards, and the Drugs and Cosmetics Act, 1940/Rules 1945 with Schedule M (revised 2023) and Schedule L-1 for testing laboratories.

Good laboratory practice: the quality system behind the number

• GLP (OECD Principles) is a quality system for the organisation and conditions of non-clinical health and environmental safety studies — planning, performance, monitoring, recording, archiving and reporting. In India, NGCMA under the DST grants and monitors GLP certification. GLP in this strict sense is *not* the same as GMP (manufacturing) or ISO/IEC 17025 (testing and calibration competence), though the disciplines overlap heavily; many Indian analytical labs informally use "GLP" to mean general good practice.
• Core GLP elements: a defined test facility management, a Study Director (single point of study control), an independent Quality Assurance Unit, written and approved SOPs for every repeated activity, a signed study plan/protocol with amendments and deviations recorded, characterised test and reference items, qualified personnel with training records, validated equipment and computerised systems, and an archive with defined retention.
• ISO/IEC 17025:2017 adds the testing-lab essentials examined in interviews: impartiality and confidentiality, metrological traceability to SI through certified reference materials and accredited calibrations, measurement uncertainty estimation and reporting, method validation and verification, decision rules for conformity statements, proficiency testing/inter-laboratory comparison, control of nonconforming work, internal audit and management review, and risk-based thinking. NABL (under the Quality Council of India) is India's accreditation body; its NABL-series documents set the specific criteria for each field and BIS/CRMs from BND (Bharatiya Nirdeshak Dravya, NPL-India) are the national reference materials.
• Documentation and data integrity — ALCOA+: data must be Attributable, Legible, Contemporaneous, Original, Accurate, plus complete, consistent, enduring and available. Practically: bound page-numbered notebooks, ink only, no overwriting or whitening — strike through once, write the correct value, initial and date with the reason; raw data (chromatograms, weighing printouts) retained; audit trails enabled in CDS software (Empower, LabSolutions, Chromeleon); unique sample IDs and chain of custody; no backdating, no "dry-labbing", no deleting a failed injection.
• Equipment control: calibration and performance verification on a schedule with status labels and due dates — analytical balance (daily internal/external weight check, annual calibration with OIML class E2/F1 weights, placed on a vibration-free table away from draughts), volumetric glassware (Class A preferred; IS/ISO tolerances), pH meter (two- or three-point buffer calibration before use), thermometers and ovens (mapping), HPLC/GC/UV (IQ-OQ-PQ qualification and system suitability before each run), pipettes (gravimetric verification).
• Quality control of results: reagent blank and method blank, duplicates and replicates, spiked recovery, matrix spike, certified reference material, control charts (Shewhart/Levey-Jennings with ±2SD warning and ±3SD action limits, Westgard rules), and a documented out-of-specification (OOS) / out-of-trend (OOT) investigation before any repeat. Report results with correct significant figures, the unit, the method reference and the uncertainty where required.
• Risk assessment before work: identify hazards, assess likelihood × severity, add controls, re-score the residual risk, record it — and for a new or scaled-up reaction run a written HIRA/JSA and get it countersigned. Induction and periodic refresher training, mock drills, incident and near-miss reporting, and a safety committee close the loop.

Key points

• GLP - a quality system for how studies are organised, performed, recorded and archived; it governs data reliability, not merely tidiness.
• ISO/IEC 17025:2017 - the international standard for testing and calibration laboratory competence; NABL accredits to it in India.
• NGCMA (DST) - India's monitoring authority for OECD GLP certification of non-clinical safety studies.
• SDS - 16-section safety data sheet; Section 4 gives first aid, Section 8 PPE and exposure limits, Section 10 incompatibilities.
• GHS - harmonised classification and labelling; nine pictograms, signal words Danger/Warning, H- and P-statements.
• NFPA 704 - blue health, red flammability, yellow reactivity, white special; 0 to 4 severity.
• Hierarchy of controls - eliminate, substitute, engineer, administer, then PPE; PPE is the last line, never the first.
• Fume hood face velocity - typically 0.4–0.6 m/s, verified before use; sash kept low as a shield.
• Acid to water - always dilute by adding acid into water with stirring and cooling; dilution of H₂SO₄ is strongly exothermic.
• Class D fire - burning metals; use special dry powder or dry sand, never water or CO₂.
• Eyewash - flush the eye for at least 15 minutes with lids held open; do not attempt chemical neutralisation on tissue.
• Flash point / LEL-UEL - lowest temperature giving an ignitable vapour, and the concentration range in air that will burn.
• LD50 / TLV-TWA - acute lethal dose (mg/kg) and the 8-hour average airborne exposure limit; lower LD50 means more toxic.
• ALCOA+ - attributable, legible, contemporaneous, original, accurate, plus complete, consistent, enduring, available.
• Traceability and uncertainty - every reported value must trace to SI through CRMs/accredited calibration and carry an uncertainty where claimed.
• Control charts - plot QC results; ±2SD warning and ±3SD action limits detect drift before it ruins a batch.
• Hazardous and Other Wastes Rules, 2016 - segregation, labelled storage, manifest and disposal only via authorised TSDF/recyclers.
• OSH Code, 2020 (in force 21 Nov 2025) - replaced the Factories Act, 1948; carries the duties on hazardous processes, health checks and records.

Formulas and examples

Example 1 — preparing 1 L of approximately 0.1 N H₂SO₄ safely.

• Concentrated H₂SO₄: 98% w/w, specific gravity 1.84, equivalent weight 49.04 g/eq.
• N = (10 × 98 × 1.84)/49.04 = 1803.2/49.04 ≈ 36.8 N.
• C₁V₁ = C₂V₂ → V₁ = (0.1 × 1000)/36.8 ≈ 2.72 mL.
• Procedure: take about 500 mL distilled water in a 1 L volumetric flask (never a dry flask), add the 2.72 mL of acid down the side with swirling and cooling, then make up to the mark after it returns to room temperature. Label: name, 0.1 N (approx.), date, preparer, expiry, and "CORROSIVE". Standardise against a primary standard before use.

Example 2 — fume hood airflow check.

• Sash open 0.40 m high over a 1.50 m wide opening → A = 0.40 × 1.50 = 0.60 m².
• Measured exhaust flow Q = 1,080 m³/h = 1,080/3,600 = 0.30 m³/s.
• v = 0.30/0.60 = 0.50 m/s — within the usual 0.4–0.6 m/s band, so acceptable.
• If the sash is raised to 0.80 m, A = 1.20 m² and v falls to 0.25 m/s — below the band, containment is lost. This is exactly why the sash is kept low.

Example 3 — exposure limit conversion for toluene.

• TLV-TWA for toluene is commonly quoted as 20 ppm (ACGIH); M = 92.14 g/mol.
• mg/m³ = ppm × M/24.45 = 20 × 92.14/24.45 = 1842.8/24.45 ≈ 75.4 mg/m³.
• A 500 mL spill evaporating into an unventilated 60 m³ store: mass = 500 mL × 0.867 g/mL ≈ 433.5 g → 433,500 mg/60 m³ ≈ 7,225 mg/m³, nearly 96 times the TWA; as a room average that is about 1,920 ppm (0.19% v/v), below the LEL of about 1.1% v/v, but the vapour near the pool is far richer and inside the flammable range — hence evacuate, kill ignition sources and ventilate, do not mop it up casually.

Example 4 — QC control chart and acceptance.

• Twenty QC results for Fe in water give x̄ = 10.2 mg/L and s = 0.30 mg/L.
• Warning limits: 10.2 ± 2(0.30) = 9.60 to 10.80 mg/L; action limits: 10.2 ± 3(0.30) = 9.30 to 11.10 mg/L.
• %RSD = 100 × 0.30/10.2 = 2.94% — acceptable for trace metals at this level.
• Today's QC reads 11.3 mg/L → outside the action limit: stop, quarantine the batch's results, investigate (standard degradation, calibration drift, contamination), correct, re-run the QC, and record the investigation. Reporting the batch without this is a data-integrity violation.

Example 5 — spiked recovery and reporting.

• Sample measures 4.0 mg/L; 2.0 mg/L of analyte is added and the spiked sample measures 5.8 mg/L.
• Recovery = 100 × (5.8 − 4.0)/2.0 = 100 × 1.8/2.0 = 90% — inside a typical 80–120% acceptance window, so the matrix is not suppressing the signal unacceptably.
• If the combined standard uncertainty is 0.25 mg/L, U = 2 × 0.25 = 0.50 → report 4.0 ± 0.5 mg/L (k = 2, approx. 95% confidence).

Where it is used

• Pharmaceutical QC and QA (Sun Pharma, Dr Reddy's, Cipla, Lupin, Zydus): analyst and QA roles built on SOP compliance, instrument qualification, ALCOA+ documentation, OOS handling and audit readiness for USFDA, EU-GMP and CDSCO inspections.
• Commercial testing and certification labs (SGS, Eurofins, TÜV SÜD, Bureau Veritas, Intertek, Vimta): NABL-accredited food, water, environmental and petroleum testing, where traceability, uncertainty and proficiency-testing performance decide whether a report is legally usable.
• Government and regulatory labs: FSSAI-notified food laboratories, state drug testing laboratories, CPCB/SPCB environmental labs, Central Water and Power Research Station, CSIR institutes (NCL, IICT, CSMCRI, NPL for CRMs and calibration) and customs/ESIC labs.
• Chemical, fertiliser, petrochemical and paint plants (Tata Chemicals, Reliance, IOCL, Asian Paints, UPL): plant laboratories operating under the OSH Code and MSIHC Rules, with on-site emergency plans, safety committees and hazardous-waste authorisation.
• Academic and research labs: institutional safety committees, biosafety and radiation safety committees (AERB licensing), chemical inventories and mandatory induction — reinforced after fatal laboratory accidents at Indian institutes led to stricter audits.
• Job roles that test this directly: QC analyst, QA/documentation officer, EHS officer, calibration engineer, lab manager, auditor and NABL/GLP consultant.

Interview questions

• Q: What is the difference between GLP, GMP and ISO/IEC 17025? A: GLP governs the conduct and recording of non-clinical safety studies, GMP governs pharmaceutical manufacture and its quality control, and ISO/IEC 17025 establishes the technical competence of testing and calibration laboratories; only 17025 formally requires measurement uncertainty and traceability statements.
• Q: You find an unlabelled bottle of clear liquid on the bench. What do you do? A: Do not open, smell or test it informally; treat it as unknown hazardous waste, isolate it in a secondary container in a hood, inform the supervisor and dispose of it through the authorised waste route with an incident record.
• Q: Why must acid be added to water and never the reverse? A: Dilution of concentrated acid is highly exothermic; adding water to acid releases the heat in a small volume, which can boil locally and eject corrosive droplets, whereas the large water mass absorbs the heat safely.
• Q: Which extinguisher would you use on a burning magnesium turning, and why not water? A: A class D dry powder or dry sand; water and CO₂ are decomposed by burning metals, liberating hydrogen or carbon and intensifying the fire.
• Q: What is ALCOA+ and give one practical violation. A: Attributable, legible, contemporaneous, original, accurate, plus complete, consistent, enduring and available; writing up readings from memory the next morning, or whitening out a value, violates contemporaneous and original.
• Q: How do you decide which glove to wear? A: From Section 8 of the SDS and a glove-manufacturer's permeation chart, choosing by breakthrough time for that specific chemical — nitrile for general acids and many solvents, butyl or Viton for chlorinated solvents, and never latex for organic solvents.
• Q: What is metrological traceability, and how is it achieved for a balance? A: An unbroken chain of calibrations linking the result to the SI unit with stated uncertainties; the balance is calibrated by an NABL-accredited agency using OIML-class weights traceable to the national standard, and checked daily with control weights.
• Q: A QC result falls outside the 3SD action limit. What is the correct sequence? A: Stop reporting, hold the batch, raise an OOS/OOT investigation covering analyst, instrument, standard, reagent and calculation, correct the assigned cause, verify with fresh QC and document everything — never simply re-inject until a passing result appears.
• Q: What does a fume hood's face velocity tell you, and what happens if the sash is raised? A: It measures the inward air speed that contains vapours, usually kept in the 0.4–0.6 m/s band; raising the sash increases the open area, so at constant exhaust flow the velocity drops and containment fails.
• Q: How is laboratory chemical waste handled legally in India? A: Segregated at source into compatible streams, stored in labelled closed containers with date records, and disposed of only through an SPCB-authorised treatment, storage and disposal facility or registered recycler under the Hazardous and Other Wastes Rules, 2016, with manifest documents for transport.
• Q: Which statute now governs occupational safety in an Indian factory laboratory? A: The Occupational Safety, Health and Working Conditions Code, 2020, in force from 21 November 2025, which has replaced the Factories Act, 1948; the detailed thresholds now sit in the central and state rules framed under the Code.
• Q: What is the hierarchy of controls, and where does PPE sit? A: Elimination, substitution, engineering controls, administrative controls and finally PPE; PPE is last because it does not reduce the hazard and fails silently if it is the wrong type, damaged or not worn.

Common mistakes

• Naming PPE first in a safety answer — examiners expect the hierarchy of controls, with PPE as the last line of defence.
• Confusing GLP with GMP or with ISO/IEC 17025, and claiming GLP accreditation when the laboratory actually holds NABL accreditation.
• Attempting to neutralise an acid or alkali burn on skin or in the eye instead of flushing with water for 15 minutes.
• Storing chemicals alphabetically, so that nitric acid ends up beside a nitro compound or acetic acid beside acetone.
• Quoting withdrawn or superseded references — the Factories Act, 1948 instead of the OSH Code, "MSDS" formats without the 16 GHS sections, or an old IS number without checking its current edition.
• Treating documentation as paperwork: unsigned raw data, backdated entries, overwritten values and disabled audit trails fail audits even when the chemistry was correct.
• Reporting a result without its unit, significant figures, method reference or uncertainty, and quietly repeating an analysis until it passes instead of raising an OOS investigation.
• Using a domestic refrigerator for solvents, overfilling waste bottles, or capping a waste container that is still generating gas.

Related topics

Volumetric and gravimetric analysis · Chromatography: HPLC, GC and TLC · Spectroscopy: UV, IR, NMR and mass · Errors, statistics and data treatment in analysis · Sampling, method validation and quality assurance · Industrial hygiene and environmental chemistry