Laboratories and small-quantity users

Laboratories are unusual chemical users. A single teaching or research lab may hold several hundred different chemicals, most in small containers of 1 L or less, many used only once or twice a year. Staff and students change often, and experiments change weekly. Small-quantity users outside labs, such as dental offices, hair salons, school science prep rooms, photo and art studios, and hospital departments, share many of the same challenges on a smaller scale. This lesson covers how storage principles apply in these settings: chemical hygiene plans, fume hoods, lab refrigerators, inventory control, and the specific risks of research work. The general hazard classes and compatibility rules from earlier lessons still apply.

Why labs are different

In a factory, a product usually arrives in large containers, is used in a fixed process and is stored in a few predictable locations. In a lab, hundreds of products arrive in small bottles, are used in changing ways and tend to accumulate. Common lab storage problems include alphabetical storage that puts incompatible chemicals side by side (acetic acid next to acetaldehyde next to ammonium nitrate), chemicals stored in fume hoods so that the hood no longer works properly, old reagents and unlabelled samples left behind by former students, peroxide formers past their dates, and household refrigerators used to store flammable solvents.

Chemical hygiene plans and lab rules

In Canada, there is no single national laboratory standard. Labs follow the general provincial occupational health and safety regulations, WHMIS requirements, the fire code, and specific rules for designated substances or controlled products. Many universities and colleges adopt a written laboratory safety program modelled on the US chemical hygiene plan concept, and CSA Z316.5, Fume hoods and associated exhaust systems, is widely used for fume hood design and testing. NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals, is also often referenced.

A chemical hygiene plan, or lab safety program, typically includes standard operating procedures for working with hazardous chemicals, criteria for using engineering controls and PPE, procedures for fume hood checks, rules for prior approval of especially hazardous work, provisions for particularly hazardous substances (carcinogens, reproductive toxins and highly toxic chemicals), training requirements, and emergency procedures. The storage parts of the plan cover segregation, quantity limits per lab, labelling, inventory, peroxide former management and waste.

Fume hoods

A chemical fume hood is a ventilated enclosure that draws air in through its opening and exhausts it outside, capturing vapours and gases released inside before they reach the worker. It is one of the most important controls in a lab, but it only works when used correctly. The speed of air entering the hood opening, called the face velocity, is a key measure of performance. Many programs specify an average face velocity of about 0.4 to 0.6 m/s (80 to 120 fpm) at the working sash height, while recognizing that face velocity alone does not prove containment. ANSI/ASSP Z9.5, Laboratory Ventilation, in the United States and CSA Z316.5 in Canada set out testing methods, including tracer gas containment testing.

Good hood practice includes: keeping the sash as low as practical, and at or below the marked working height; working at least 15 cm (6 in) inside the hood; keeping the hood free of clutter and stored chemicals, which disrupt airflow; not putting your head inside the hood; checking the airflow monitor before each use; and having hoods tested at least annually and after any change to the ventilation system. A fume hood is not a storage cabinet; bottles left in the hood become fuel if a fire starts there.

# Average a fume hood face velocity traverse and flag uneven readings.
# Nine grid readings in m/s at the working sash height (illustrative).
readings = [0.52, 0.48, 0.55, 0.47, 0.50, 0.58, 0.30, 0.45, 0.51]
avg = sum(readings) / len(readings)
print(f"Average face velocity: {avg:.2f} m/s ({avg * 196.85:.0f} fpm)")
print("Within typical 0.4-0.6 m/s target:", 0.4 <= avg <= 0.6)
for i, v in enumerate(readings, 1):
    dev = (v - avg) / avg * 100
    note = "  <- check: more than 20% below average" if dev < -20 else ""
    print(f"point {i}: {v:.2f} m/s ({dev:+5.1f}%){note}")

Average face velocity: 0.48 m/s (95 fpm)
Within typical 0.4-0.6 m/s target: True
point 1: 0.52 m/s ( +7.3%)
point 2: 0.48 m/s ( -0.9%)
point 3: 0.55 m/s (+13.5%)
point 4: 0.47 m/s ( -3.0%)
point 5: 0.50 m/s ( +3.2%)
point 6: 0.58 m/s (+19.7%)
point 7: 0.30 m/s (-38.1%)  <- check: more than 20% below average
point 8: 0.45 m/s ( -7.1%)
point 9: 0.51 m/s ( +5.3%)

The traverse average is within the typical target, but one reading in the lower corner is far below the others. That pattern often means something is blocking the airflow near that point, such as equipment pushed against the baffle, bottles stored at the back, or a damaged baffle slot. The fix is to clear the hood and retest, and if the low reading persists, to ask the ventilation contractor to check the baffles and exhaust. The 20 per cent flag used here is an illustrative screening rule, not a value from a standard.

Laboratory refrigerators and freezers

Ordinary household refrigerators contain light switches, thermostats and defrost heaters inside the storage compartment that can ignite flammable vapours from leaking solvent bottles. Many lab explosions have started this way. Flammable solvents, and samples containing them, must be stored only in refrigerators designed for the purpose: laboratory-safe or flammable-material storage refrigerators have no ignition sources inside the compartment, while explosion-proof units are designed for use in locations where flammable vapour may be present outside the unit too. Label every refrigerator with what it may hold, and never store food or drink in a lab refrigerator.

Inventory and ordering

A good chemical inventory is the foundation of lab storage safety. It lets people find what they need instead of buying more, it supports peroxide dating and expiry checks, it shows emergency responders what is in each room, and it is the basis for checking quantity limits under the fire code and NFPA 45. Many institutions use a barcode-based system that records each container at receipt and removes it when emptied or discarded. An annual physical reconciliation, in which every container is scanned and orphans are removed, keeps the inventory honest.

Ordering policies help as much as storage rules. Encourage users to buy the smallest container that will last the project, to check the inventory and shared stock before ordering, and to avoid bulk discounts that leave years of supply on the shelf. Some institutions run a chemical redistribution program so unopened surplus can be reused rather than discarded.

Research hazards and scale-up

Research labs sometimes work with new or poorly characterized materials. In 2010, a graduate student at Texas Tech University was seriously injured when a compound he was preparing, an energetic material, detonated after he made a much larger batch than his group had previously handled. The US Chemical Safety Board investigated and found weaknesses in hazard evaluation, in the management of physical hazards in research labs, and in learning from earlier near misses. The lessons apply to storage as well as to experiments: new and energetic materials should be stored in small quantities, in labelled containers, in locations approved by the safety office, and scale-up should require a documented hazard review.

Small-quantity users outside labs

Hair salons store oxidizing developers (hydrogen peroxide), ammonia-based dyes, acetone nail polish remover and flammable aerosol sprays. Dental offices use acrylic monomers, disinfectants and small cylinders of nitrous oxide and oxygen. School science prep rooms often hold decades-old stock, including chemicals that should no longer be in schools at all. The same principles apply in all of these places: keep an inventory, buy small, segregate oxidizers from flammables and acids from bases, use a small flammable cabinet for solvents and aerosols, keep cylinders chained, provide an eyewash where corrosives are used, and dispose of old stock properly.

Closing out a lab

When a researcher leaves, a lab is renovated, or a program ends, chemicals can be abandoned in large numbers. A lab close-out procedure prevents this. Before the departure date, the responsible person reviews the inventory, transfers useful chemicals to a named new owner, labels everything clearly, and arranges disposal of the rest through the waste program. The safety office then inspects the lab, checks fume hoods, refrigerators and cabinets for leftover materials, and signs off before the space is reassigned or handed to contractors. Contractors should never be the first people to open an old lab cabinet, because they may not recognize peroxide formers, reactive metals or unlabelled toxic materials.