Safety RAMP • Recognize hazards • Assess the risks of the hazards • Minimize the risks • Prepare for emergencies Types of hazards • Physical hazards • Chemical hazards • Health hazards • Reactive hazards Physical Hazards • Electricity • Compressed gases • Heat: Hot plates, ovens • Cold: Liquid N2, dry ice • Radiation: X-rays • Asphyxiation: N2, Ar, He Special chemical hazards every chemist should know • • • • • • • • • • • • • Powerful acids: HCl(aq), HNO3, H2SO4, concentrated acetic acid Powerful bases: NaOH, KOH, NH3(aq) Powerful oxidizers: perchloric acid, O2, nitrates, Br2 Flammable liquids, esp. organic solvents Poisonous gases: HCN, Zn fumes, H2, NH3, Cl2, HCl(g), NO2 HF(aq) Peroxides, esp. in ethers Cyanides with acids Heavy metals, esp. mercury Radioactive materials Pyrophoric materials, esp. Na & K Explosive powders: sugar, wheat, Al, Mg Hg compounds, esp. organic mercury compounds Fire • What is fire? • The fire triangle • Types of fires and their extinguishers: A, B, C, D Fire is rapid oxidation of a fuel, with emission of light and heat. The fire triangle Fuel: Hydrocarbons, H2, NH3, metal powder, wood, NH4NO3, etc. Oxidizer: Air, O2, F2, N2O, NaNO3, NH4NO3, H2O2 Ignition: Spark, flame, UV light, friction Hypergolic materials ignite on contact—no ignition. Types of fires and extinguishers Fire • Extinguish or evacuate? • Policy at York is to discourage extinguishing, even though we are required to have fire extinguishers. • Before evacuating, notify relevant people (instructor or Public Safety at York) Health Hazards • Acute (brief) exposure: mainly strong reagents • Chronic (long term) exposure: mainly weak reagents Reaction Hazards • Incompatible chemicals Don’t store acids with bases Don’t store oxidizers with reducers Don’t store acids with cyanides • Catalysts: Runaway reactions • Explosives • Pyrophoric chemicals Labels NFPA Diamond High numbers are worse! Globally Harmonized System (GHS) GHS language includes: • A signal word (such as “danger” or “warning”) • A symbol or pictogram (such as a flame within a red-bordered diamond) • A hazard statement (such as “causes serious eye damage”) • Precautionary statements for safely using the chemical • • • • 17 physical hazard classes 10 health hazard classes 2 environmental hazard classes Low numbers are worse! Globally Harmonized System (GHS) Safety Data Sheets (SDS) Safety Data Sheets (SDS) • • • • • Used to be called Material Safety Data Sheet (MSDS) Legal and technical content More recent versions are generally more useful Available for anything you buy Format is specified, but content is not; every company can generate its own • Must be made available to all employees in a print copy Safety Data Sheets (SDS) Examine sucrose SDS. Chemtrec = company with hazmat incident response phone number CAS number ACGIH = American Conference of Governmental Industrial Hygienists TWA = time-weighted average PEL = permitted exposure limit LD50 = dose lethal to 50% of population IARC = International Agency for Research on Cancer NTP = National Toxicology Program OSHA = Federal Occupational Safety and Health Administration Minimize Risks Ventilation Air turnover in the lab should be 6 air changes per hour. Supply air intake should be far from all exhausts. Put stuff as far to the back as you can manage, and don’t block the air flow. Personal protective equipment • Gloves • Eye protection: goggles, safety glasses, contact lenses, prescription glasses • Lab coats and aprons • Face masks (respirators), face shields for splashes and heat Mill gloves for handling hot glassware and crucibles, or dry ice Respirators and face masks Face shield Furnace face shield. The thin gold coating reflects IR. Prepare • Fire • Electrical shock • Burns from contact with hot objects • Chemical burns • Cuts • Strong reagent spills Electrical Shock Current determines damage, not voltage. Usually, anything above 0.1 A is dangerous. Houses are typically wired for 200 A, labs for more. You can feel as little as 1 mA. For a constant voltage, the current is determined by resistance. Air and dirt are good insulators. Water and metal are good conductors. Circuit breakers and fuses break a circuit if the current goes above a limit. The limit is usually far above fatality. These devices prevent property damage and fires. They don’t protect people. Current causes muscle contraction, making it hard to let go. Involuntary screaming. Do not touch a person being shocked—turn off the power! Waste What is waste? When it leaves the experimental setup Waste consolidated from several labs; pick-up by special contractors; how do they dispose of it? Separation of waste to reduce interactions (chemical reactions) among the waste, and sometimes to make money Read labels and use your chemistry knowledge to make good choices. Don’t mix acids with bases, oxidizers with reducers, cyanides with acids, etc. Other resources:
