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Gases, Vapors and Solvents HS 432

Gases, Vapors and Solvents HS 432. HS 432. Definitions. Gases Materials in the gaseous state at NTP (25 C, 1 atm). Vapors Chemicals that are liquids at NTP will exist partially in the gaseous phase; that portion is called vapor. Vapor pressure (VP)

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Gases, Vapors and Solvents HS 432

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  1. Gases, Vapors and SolventsHS 432 HS 432

  2. Definitions • Gases • Materials in the gaseous state at NTP (25 C, 1 atm). • Vapors • Chemicals that are liquids at NTP will exist partially in the gaseous phase; that portion is called vapor. • Vapor pressure (VP) • Concentration of the chemical in air when an equilibrium is established between the liquid phase and the gaseous (vapor) stage. • VP increases as temperature increases

  3. Definitions • Gases • Materials in the gaseous state at NTP (25 C, 1 atm). • Vapors • Chemicals that are liquids at NTP will exist partially in the gaseous phase; that portion is called vapor. • Vapor pressure (VP) • Concentration of the chemical in air when an equilibrium is established between the liquid phase and the gaseous (vapor) stage. • VP increases as temperature increases

  4. Solvent • Solvents are liquids in which something, called a solute, can be dissolved; solids may also be suspended in solvents. • Water is a solvent • Organic materials are solvents • Solvents can be volatile • Highly volatile solvents or high vapor pressures will be inhaled easily. • Solvents can be highly polar (water) or soluble. Solubility is very important in understanding the hazards presented by various solvents as solubility affects absorption into the body, distribution throughout the body, storage in various tissues, and elimination of chemicals. • More fat soluble solvents will penetrate the skin easier. • Water and fat soluble solvents will be absorbed easier.

  5. Critical Exposure Factors • 1. Mode of use and potential for exposure • e.g. ventilation, spray vs. rolling applications of paint. • 2. Temperature and volatility • Temperature affects vapor pressure and potential for inhalation. • Airborne concentration of a solvent vapor depends on the vapor pressure, which is a measure of the volatility of the solvent. • Vapor pressure of nay chemical compound is directly related to the temperature. • 3. Concentration • 4. Reactivity • Can enhance or reduce health hazard. • 5. Toxicity & Exposure guidelines • PEL, TLV, REL

  6. 1. Compressed gases Falls may result in projectile hazard. Carefully transport and avoid heat. 2. Gases 3. Cryogenic liquids Frostbite hazard. Vaporize rapidly + denser than air  potential for oxygen deficiency in confined spaces Material Safety Data Sheets (p. 144-147, p. 155-156) Hazards of Gases, Vapors & Solvents

  7. 4. Flammability, explosion & reactivity Flash point The lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near the surface of the liquid. Flammable liquids Flash point below 100 F Combustible liquids Flash point above 100 F Fire point The lowest temperature at which vapors of a liquid evolve fast enough to support continuous combustion. Is usually 5 F above flash point Flammable range (explosive range) Includes all the concentrations of a vapor in air between the LFL (LEL) and the UFL (UEL). LFL: concentration of a liquid vapor in air below which flame propagation does not occur because mixture is too lean. UFL: concentration of a liquid vapor in air above which flame propagation does not occur because mixture is too rich. E.g. LEL% too small only a small amount of vapor in the air is ignitable Hazards of Gases, Vapors & Solvents

  8. Toxicological Effects • Site of action • May be local or systemic • Water-soluble gases may cause respiratory irritation • Less water-soluble gases may cause edema and pulmonary problems later • Skin absorption may lead to systemic effects • 2. Asphyxiation • Simple asphyxiants: Gases & vapors may replace oxygen in the air • Minimum O2 conc. required for life is 18% • Chemical asphyxiants: react with cells to disrupt O2 transport • E.g. Hydrogen sulfide, hydrogen cyanide

  9. Toxicological Effects • Organic & inorganic gases • Reactivity is important • Warning properties may be poor (asphyxiation hazard) • 4. Inorganic acids & bases • Corrosive, can burn skin and mucous membranes ( • E.g. HCL, HNO3, H2SO4, HF • PPE important • 5. Other aqueous solutions & systems • May cause contact dermatitis • Solvents & solvent vapors • Organic solvents have a wide range of toxic effects • Contact with skin may cause irritation, defatting, dermatitis • Less soluble solvents may be systemically absorbed to damage organs such as liver, kidneys, CNS.

  10. Control of Hazards • Process controls • Selection of chemicals • Engineering controls • Enclosure • Ventilation • Personal protective equipment • Respirators • Protective clothing and gloves • Protective eyewear

  11. 1. Compressed gases Falls may result in projectile hazard. Carefully transport and avoid heat. 2. Gases 3. Cryogenic liquids Frostbite hazard. Vaporize rapidly + denser than air  potential for oxygen deficiency in confined spaces Material Safety Data Sheets (p. 144-147, p. 155-156) Hazards of Gases, Vapors & Solvents

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