habitat is the place or type of ecosystem in which a microorganism, fungal, plant or animal species is commonly found integrated into a community, an interactive system of living organisms. Habitat fulfils the requirements of the living organisms inhabitating a delineated part of the aquatic or terrestrial environment.
hazard analysis and critical control points, or HACCP is a systematic preventive approach to food safety and pharmaceutical safety that identifies physical, chemical, and biological hazards in production processes that can cause the finished product be unsafe, and designs measurements to reduce these risks to a safe level. In this manner, HACCP is referred as the prevention of hazards rather than finished product inspection.
The HACCP system can be used at all stages of a food chain, from food production and preparation processes including packaging, distribution, etc. HACCP is believed to stem from of a production process monitoring used during World War II because traditional "end of the pipe" testing on artillery shell's firing mechanisms could not be performed and a large percent of the artillery shells be made at the time were either duds or misfiring.
HACCP has been recognized internationally as a logical tool for adapting traditional inspection methods to a modern, science-based, food safety system. Based on risk-assessment, HACCP plans allow both industry and government to allocate their resources efficiently in establishing and auditing safe food production practices. In 1994, the organization of International HACCP Alliance was established initially for the US meat and poultry industries to assist them with implementing HACCP and now its membership has been spread over other professional/industrial areas.
Hence, HACCP has been increasingly applied to industries other than food, such as cosmetics and pharmaceuticals. This method, which in effect seeks to plan out unsafe practices based on science, differs from traditional "produce and sort" quality control methods that do nothing to prevent hazards from occuring and must identify them at the end of the process. HACCP is focused only on the health safety issues of a product and not the quality of the product, yet HACCP principles are the basis of most food quality and safety assurance systems. FAO/WHO published a guideline for all governments to handle the issue in small and less developed food businesses.
the HACCP seven principles
Principle 1: Conduct a hazard analysis. – Plans determine the food safety hazards and identify the preventive measures the plan can apply to control these hazards. A food safety hazard is any biological, chemical, or physical property that may cause a food to be unsafe for human consumption.
Principle 2: Identify critical control points. – A critical control point (CCP) is a point, step, or procedure in a food manufacturing process at which control can be applied and, as a result, a food safety hazard can be prevented, eliminated, or reduced to an acceptable level.
Principle 3: Establish critical limits for each critical control point. – A critical limit is the maximum or minimum value to which a physical, biological, or chemical hazard must be controlled at a critical control point to prevent, eliminate, or reduce to an acceptable level.
Principle 4: Establish critical control point monitoring requirements. – Monitoring activities are necessary to ensure that the process is under control at each critical control point. In the United States, the FSIS is requiring that each monitoring procedure and its frequency be listed in the HACCP plan.
Principle 5: Establish corrective actions. – These are actions to be taken when monitoring indicates a deviation from an established critical limit. The final rule requires a plant's HACCP plan to identify the corrective actions to be taken if a critical limit is not met. Corrective actions are intended to ensure that no product injurious to health or otherwise adulterated as a result of the deviation enters commerce.
Principle 6: Establish procedures for ensuring the HACCP system is working as intended. – Validation ensures that the plants do what they were designed to do; that is, they are successful in ensuring the production of a safe product. Plants will be required to validate their own HACCP plans. FSIS will not approve HACCP plans in advance, but will review them for conformance with the final rule.
Verification ensures the HACCP plan is adequate, that is, working as intended. Verification procedures may include such activities as review of HACCP plans, CCP records, critical limits and microbial sampling and analysis. FSIS is requiring that the HACCP plan include verification tasks to be performed by plant personnel. Verification tasks would also be performed by FSIS inspectors. Both FSIS and industry will undertake microbial testing as one of several verification activities.
Verification also includes "validation" – the process of finding evidence for the accuracy of the HACCP system (e.g. scientific evidence for critical limitations).
Principle 7: Establish record keeping procedures. – The HACCP regulation requires that all plants maintain certain documents, including its hazard analysis and written HACCP plan, and records documenting the monitoring of critical control points, critical limits, verification activities, and the handling of processing deviations.
harmful substances are those which endanger living organisms, natural and man-mad environmnet with their potential adverse effects. We also use the following terms for these substances: dangerous substances, substances with adverse effects. We can specify the advers effect and the harm, e.g.: explosives, flammable substances or preparations, oxidising or reducing agents, acidic or alkaline substances, toxic substances or preparations, corrosive substances or preparations irritants, sensitizers, carcinogenic, mutagenic, reprotoxici or dangerous for the environment. The substances which pose harm on the local and global environment are mainly those which poison water and soil, cause acid-rain, CO2 and methane overproduction or ozone depletion, etc.
See also: dangerous substances, toxic substance, toxic metals, toxic effect, toxicity, mutagenic effect, mutagenicity, reprotoxic
the hazard is a property or set of properties, that make a substance dangerous. (Source: REACH Glossary)
hazard assessment consists in using the information about the intrinsic properties of the substance to make an assessment of hazard in the following areas:
1. Human health hazard assessment
2. Human health hazard assessment of physicochemical properties
3. Environmental hazard assessment
4. PBT and vPvB assessment. (Source, REACH Glossary)
Hazard assessment has two steps, hazard identification and establishment of dose-response relationship for observed adverse effects in the specified (eco)toxicological endpoints.
the type of hazard is described by hazard classes. Generally these are subdivided into hazard categories which express the level of hazardousness.
Altogether the GHS comprises 16 classes for physical-chemical hazards, 10 classes for health hazards, and one class for hazards to the aquatic environment.
hazard statements are standardized phrases about the hazards of chemical substances and mixtures. It is part of GHS, the Globally Harmonized System (GHS) of Classification and Labelling of Chemicals (CLP)
After the harmonisation of GHS and CLP hazard statements replace R-phrases (used by DSD (Dangerous Substance Directive)
Hazard statements are one of the elements of labelling chemicals in CLP and GHS, which are:
- identification of the chemical substance or other material or product containing cgemicals
- one or more hazard pictograms
- a signal word – either DANGER or WARNING – where necessary
- precautionary statements, indicating how the product should be handled to minimize risks to the user and the environment
- the identity of the supplier: manufacturer or importer
Hazard statements for physico-chemical, human health and environmental hazards the following:
- H200: Unstable explosive
- H201: Explosive; mass explosion hazard
- H202: Explosive; severe projection hazard
- H203: Explosive; fire, blast or projection hazard
- H204: Fire or projection hazard
- H205: May mass explode in fire
- H220: Extremely flammable gas
- H221: Flammable gas
- H222: Extremely flammable material
- H223: Flammable material
- H224: Extremely flammable liquid and vapour
- H225: Highly flammable liquid and vapour
- H226: Flammable liquid and vapour
- H227: Combustible liquid
- H228: Flammable solid
- H240: Heating may cause an explosion
- H241: Heating may cause a fire or explosion
- H242: Heating may cause a fire
- H250: Catches fire spontaneously if exposed to air
- H251: Self-heating; may catch fire
- H252: Self-heating in large quantities; may catch fire
- H260: In contact with water releases flammable gases which may ignite spontaneously
- H261: In contact with water releases flammable gas
- H270: May cause or intensify fire; oxidizer
- H271: May cause fire or explosion; strong oxidizer
- H272: May intensify fire; oxidizer
- H280: Contains gas under pressure; may explode if heated
- H281: Contains refrigerated gas; may cause cryogenic burns or injury
- H290: May be corrosive to metals
Human health hazard
- H300: Fatal if swallowed
- H301: Toxic if swallowed
- H302: Harmful if swallowed
- H303: May be harmful if swallowed
- H304: May be fatal if swallowed and enters airways
- H305: May be harmful if swallowed and enters airways
- H310: Fatal in contact with skin
- H311: Toxic in contact with skin
- H312: Harmful in contact with skin
- H313: May be harmful in contact with skin
- H314: Causes severe skin burns and eye damage
- H315: Causes skin irritation
- H316: Causes mild skin irritation
- H317: May cause an allergic skin reaction
- H318: Causes serious eye damage
- H319: Causes serious eye irritation
- H320: Causes eye irritation
- H330: Fatal if inhaled
- H331: Toxic if inhaled
- H332: Harmful if inhaled
- H333: May be harmful if inhaled
- H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled
- H335: May cause respiratory irritation
- H336: May cause drowsiness or dizziness
- H340: May cause genetic defects
- H341: Suspected of causing genetic defects
- H350: May cause cancer
- H351: Suspected of causing cancer
- H360: May damage fertility or the unborn child
- H361: Suspected of damaging fertility or the unborn child
- H362: May cause harm to breast-fed children
- H370: Causes damage to organs
- H371: May cause damage to organs
- H372: Causes damage to organs through prolonged or repeated exposure
- H373: May cause damage to organs through prolonged or repeated exposure
- H400: Very toxic to aquatic life
- H401: Toxic to aquatic life
- H402: Harmful to aquatic life
- H410: Very toxic to aquatic life with long lasting effects
- H411: Toxic to aquatic life with long lasting effects
- H412: Harmful to aquatic life with long lasting effects
- H413: May cause long lasting harmful effects to aquatic life
Some other EU-specific hazard statements:
- EUH001: Explosive when dry
- EUH006: Explosive with or without contact with air
- EUH014: Reacts violently with water
- EUH018: In use may form flammable/explosive vapour-air mixture
- EUH019: May form explosive peroxides
- EUH044: Risk of explosion if heated under confinement
- EUH029: Contact with water liberates toxic gas
- EUH031: Contact with acids liberates toxic gas
- EUH032: Contact with acids liberates very toxic gas
- EUH066: Repeated exposure may cause skin dryness or cracking
- EUH070: Toxic by eye contact
- EUH071: Corrosive to the respiratory tract
- EUH059: Hazardous to the ozone layer
- EUH201: Contains lead. Should not be used on surfaces liable to be chewed or sucked by children.
- EUH201A: Warning! Contains lead.
- EUH202: Cyanoacrylate. Danger. Bonds skin and eyes in seconds. Keep out of the reach of children.
- EUH203: Contains chromium(VI). May produce an allergic reaction.
- EUH204: Contains isocyanates. May produce an allergic reaction.
- EUH205: Contains epoxy constituents. May produce an allergic reaction.
- EUH206: Warning! Do not use together with other products. May release dangerous gases (chlorine).
- EUH207: Warning! Contains cadmium. Dangerous fumes are formed during use. See information supplied by the manufacturer. Comply with the safety instructions.
- EUH208: Contains <name of sensitising substance>. May produce an allergic reaction.
- EUH209: Can become highly flammable in use.
- EUH209A: Can become flammable in use.
- EUH210: Safety data sheet available on request.
- EUH401: To avoid risks to human health and the environment, comply with the instructions for use.
Source: CLP Regulation
hazard warning may be any word, picture, symbol, or combination thereof appearing on a label or other appropriate form of warning which convey the hazards of the chemical(s) in the container(s) or trasport facility.
wastes on the List of Wastes are hazardous if they have one or more of the following hazardous properties:
H1 “Explosive”: substances and preparations which may explode under the effect of flame or that are more sensitive to shocks or friction than dinitrobenzene.
H2 “Oxidising”: substances and preparations which exhibit highly exothermic reactions when in contact with other substances, particularly flammable substances.
H3A Highly flammable (first indent): liquid substances and preparations having a flash point below 21oC (including extremely flammable liquids), or
H3A Highly flammable (second indent): Substances and preparations which may become hot and finally catch fire in contact with air at ambient temperature without any application of energy, or
H3A Highly flammable (third indent): solid substances and preparations which may readily catch fire after brief contact with a source of ignition and which continue to burn or to be consumed after removal of the ignition source, or
H3A Highly flammable (fourth indent): gaseous substances and preparations which are flammable in air at normal temperature and pressure, or
H3A Highly flammable (fifth indent): substances and preparations which, in contact with water or damp air, evolve highly flammable gases in dangerous quantities.
H3B “Flammable”: liquid substances and preparations having a flash point equal to or greater than 21 0C and less than or equal to 55oC.
H4 “Irritant”: non-corrosive substances and preparations which, through immediate, prolonged or repeated contact with the skin or mucous membrane, can cause inflammation.
H5 “Harmful”: substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may involve limited health risks.
H6 “Toxic”: substances and preparations (including very toxic substances and preparations) which, if they are inhaled or ingested or if they penetrate the skin, may involve serious, acute or chronic health risks and even death.
H7 “Carcinogenic”: substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce cancer or increase its incidence.
H8 “Corrosive”: substances and preparations which may destroy living tissue on contact.
H9 “Infectious”: substances containing viable micro-organisms or their toxins which are known or reliably believed to cause disease in man or other living organisms.
H10 “Teratogenic”: substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce non-hereditary congenital malformations or increase their incidence.
H11 “Mutagenic”: substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce hereditary genetic defects or increase their incidence.
H12 Substances and preparations which release toxic or very toxic gases in contact with water, air or an acid.
H13 Substances and preparations capable by any means, after disposal, of yielding another substance, e.g. a leachate, which possesses any characteristics listed above.
H14 “Ecotoxic”: substances and preparations which present or may present immediate or delayed risks for one or more sectors of the environment.
categories or generic types of hazardous waste listed according to their nature or the activity which generated them (waste may be liquid, sludge or solid in form):
Annex I. A.
1. anatomical substances; hospital and other clinical wastes;
2. pharmaceuticals, medicines and veterinary compounds;
3. wood preservatives;
4. biocides and phyto-pharmaceutical substances;
5. residue from substances employed as solvents;
6. halogenated organic substances not employed as solvents excluding inert polymerized materials;
7. tempering salts containing cyanides;
8. mineral oils and oily substances (e.g. cutting sludges, etc.);
9. oil/water, hydrocarbon/water mixtures, emulsions;
10. substances containing PCBs and/or PCTs (e.g. dielectrics etc.);
11. tarry materials arising from refining, distillation and any pyrolytic treatment (e.g. still bottoms, etc.);
12. inks, dyes, pigments, paints, lacquers, varnishes;
13. resins, latex, plasticizers, glues/adhesives;
14. chemical substances arising from research and development or teaching activities which are not identified and/or are new and whose effects on man and/or the environment are not known (e.g. laboratory residues, etc.);
15. pyrotechnics and other explosive materials;
16. photographic chemicals and processing materials;
17. any material contaminated with any congener of polychlorinated dibenzo-furan;
18. any material contaminated with any congener of polychlorinated dibenzo-p-dioxin.
19. animal or vegetable soaps, fats, waxes;
20. non-halogenated organic substances not employed as solvents;
21. inorganic substances without metals or metal compounds;
22. ashes and/or cinders;
23. soil, sand, clay including dredging spoils;
24. non-cyanidic tempering salts;
25. metallic dust, powder;
26. spent catalyst materials;
27. liquids or sludges containing metals or metal compounds;
28. residue from pollution control operations (e.g. baghouse dusts, etc.) except (29), (30) and (33);
29. scrubber sludges;
30. sludges from water purification plants;
31. decarbonization residue;
32. ion-exchange column residue;
33. sewage sludges, untreated or unsuitable for use in agriculture;
34. residue from cleaning of tanks and/or equipment;
35. contaminated equipment;
36. contaminated containers (e.g. packaging, gas cylinders, etc.) whose contents included one or more of the constituents listed in Annex II;
37. batteries and other electrical cells;
38. vegetable oils;
39. materials resulting from selective waste collections from households and which exhibit any of the characteristics listed in Annex III;
40. any other wastes which contain any of the constituents listed in Annex II and any of the properties listed in Annex III.
Wastes having as constituents:
C1 beryllium; beryllium compounds;
C2 vanadium compounds;
C3 chromium (VI) compounds;
C4 cobalt compounds;
C5 nickel compounds;
C6 copper compounds;
C7 zinc compounds;
C8 arsenic; arsenic compounds;
C9 selenium; selenium compounds;
C10 silver compounds;
C11 cadmium; cadmium compounds;
C12 tin compounds;
C13 antimony; antimony compounds;
C14 tellurium; tellurium compounds;
C15 barium compounds; excluding barium sulfate;
C16 mercury; mercury compounds;
C17 thallium; thallium compounds;
C18 lead; lead compounds;
C19 inorganic sulphides;
C20 inorganic fluorine compounds, excluding calcium fluoride;
C21 inorganic cyanides;
C22 the following alkaline or alkaline earth metals: lithium, sodium, potassium, calcium, magnesium in uncombined form;
C23 acidic solutions or acids in solid form;
C24 basic solutions or bases in solid form;
C25 asbestos (dust and fibres);
C26 phosphorus: phosphorus compounds, excluding mineral phosphates;
C27 metal carbonyls;
C32 PCBs and/or PCTs;
C33 pharmaceutical or veterinary coumpounds;
C34 biocides and phyto-pharmaceutical substances (e.g. pesticides, etc.);
C35 infectious substances;
C37 isocyanates; thiocyanates;
C38 organic cyanides (e.g. nitriles, etc.);
C39 phenols; phenol compounds;
C40 halogenated solvents;
C41 organic solvents, excluding halogenated solvents;
C42 organohalogen compounds, excluding inert polymerized materials and other substances referred to in this Annex;
C43 aromatic compounds; polycyclic and heterocyclic organic compounds;
C44 aliphatic amines;
C45 aromatic amines C46 ethers;
C47 substances of an explosive character, excluding those listed elsewhere in this Annex;
C48 sulphur organic compounds;
C49 any congener of polychlorinated dibenzo-furan;
C50 any congener of polychlorinated dibenzo-p-dioxin;
C51 hydrocarbons and their oxygen; nitrogen and/or sulphur compounds not otherwise taken into account in this Annex.
Certain duplications of generic types of hazardous wastes listed in Annex I are intentional.
the waste properties of wastes are enlisted here:
H1 "Explosive": substances and preparations which may explode under the effect of flame or which are more sensitive to shocks or friction than dinitrobenzene.
H2 "Oxidizing": substances and preparations which exhibit highly exothermic reactions when in contact with other substances, particularly flammable substances.
H3-A "Highly flammable":
- liquid substances and preparations having a flash point below 21 °C (including extremely flammable liquids), or
- substances and preparations which may become hot and finally catch fire in contact with air at ambient temperature without any application of energy, or
- solid substances and preparations which may readily catch fire after brief contact with a source of ignition and which continue to burn or to be consumed after removal of the source of ignition, or
- gaseous substances and preparations which are flammable in air at normal pressure, or
- substances and preparations which, in contact with water or damp air, evolve highly flammable gases in dangerous quantities.
H3-B "Flammable": liquid substances and preparations having a flash point equal to or greater than 21 °C and less than or equal to 55 °C.
H4 "Irritant": non-corrosive substances and preparations which, through immediate, prolonged or repeated contact with the skin or mucous membrane, can cause inflammation.
H5 "harmful": substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may involve limited health risks.
H6 "Toxic": substances and preparations (including very toxic substances and preparations) which, if they are inhaled or ingested or if they penetrate the skin, may involve serious, acute or chronic health risks and even death.
H7 "Carcinogenic": substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce cancer or increase its incidence.
H8 "Corrosive": substances and preparations which may destroy living tissue on contacts.
H9 "Infectious": substances containing viable micro-organisms or their toxins which are known or reliably believed to cause disease in man or other living organisms.
H10 "Teratogenic": substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce non-hereditary congenital malformations or increase their incidence.
H11 "Mutagenic": substances and preparations which, if they are inhaled or ingested or if they penetrate the skin, may induce hereditary genetic defects or increase their incidence.
H12 Substances and preparations which release toxic or very toxic gases in contact with water, air or an acid.
H13 Substances and preparations capable by any means, after disposal, of yielding another substance, e.g. a leachate, which possesses any of the characteristics listed above.
H14 "Ecotoxic": substances and preparations which present or may present immediate or delayed risks for one or more sectors of the environment.
1. Attribution of the hazard properties "toxic" (and "very toxic"), "harmful", "corrosive" and "irritant" is made on the basis of the criteria laid down by Annex VI, part I A and part II B, of Council Directive 67/548/EEC of 27 June 1967 of the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (1), in the version as amended by Council Directive 79/831/EEC (2).
2. With regard to attribution of the properties "carcinogenic", "teratogenic" and "mutagenic", and reflecting the most recent findings, additional criteria are contained in the Guide to the classification and labelling of dangerous substances and preparations of Annex VI (part II D) to Directive 67/548/EEC in the version as amended by Commission Directive 83/467/EEC (1).
Hazard and Operability Study.
hydrochlorofluorocarbon, a colorless gas, better known as HCFC-22, R-22. It was once commonly used as a propellant and in air conditioning applications. These applications are being phased out due to ozone depletion potential and status as a potent greenhouse gas. R22 is a versatile intermediate in industrial organofluorine chemistry, e.g. as a precursor to tetrafluoroethylene.
high-density polyethylene (HDPE) is plastic that is used predominantly in the manufacture of blow-molded bottles for milk and household cleaners and injection-molded pails, bottle caps, appliance housings, and toys.
Special, environmnetal application of HDPE is in form of geomembrane, used for isolation in environmental technologies, such as lining in reservoirs, waste disposal sites, lakes, etc.
the concentration of the volatile molecules in the vapour space above a sample is proportional to the concentration in the sample. Certain methods sample this vapour (headspace analysis).
a kind of gas chromatography sampling the headspace above a sample. The composition in the headspace gives information on the composition of the sample. Suitable for the analyis of volatile components such as VOC, BTEX.
noise consequences on human health consist in loss of hearing and psychological effects.
a physical agent, a chemical substance or a biological organism has health hazard, for which there is statistically significant evidence that acute or chronic health effects may occur in exposed organisms or humans. This evidence should be based on at least one study conducted in accordance with established scientific principles, standardised test methods or epidemiological studies.
There are numerous health hazards that can affect people in their natural environment or at their workplace. According to these two categories we distinguish environmnetal helath hazard and occupational health hazard.
Examples of environmental health hazards may be:
There are numerous health hazards that can affect people in their natural environment. Examples of environmental health hazards enlisted by Wikipedia and completed by authors, are the following:
- air pollution
- antibiotic agents in animals destined for human consumption
- antibiotic resistance
- arsenic - a contaminant of fresh water sources (water wells)
- asbestos - carcinogenic
- avian influenza
- bovine spongiform encephalopathy (BSE)
- chemical substances (many different substances with a wide range of effects)
- climate change
- cosmic rays
- electromagnetic fields and radiation
- environmental pollution
- endocrine disruptors
- explosive material
- extreme weather
- food poisoning
- global warming
- heavy metals
- hormones in animals destined for human consumption
- ionisation radiation
- lead in paint
- light pollution
- marine debris
- noise pollution
- onchocerciasis (river blindness)
- pollen for allergic people
- polychlorinated biphenyls
- radon and other natural sources of radioactivity
- severe acute respiratory syndrome (SARS)
- sick building syndrome
- soil pollution
- tobacco smoking
- toxic waste
- ultraviolet light
- water pollution
- waste disposal, illegal
a decrease in strength or any abnormality or partial or complete loss of hearing or of the function of ear, or hearing system, due directly or secondarily to pathology or injury; it may be either temporary or permanent.
the total of measures and devices implemented to preserve persons from harm to the faculty of perceiving sound.
body of surface water which as a result of physical alterations by human activity is substantially changed in character, as designated by the Member State in accordance with the provisions of Annex II. of the Water Framework Directive.
hectare is a unit of area, defined as 10,000 square metres, and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare ("hecto-" + "are") was thus 100 ares or 1/100 km2. Data in the table supports conversion of different area units.
|hectares||acres||2.471 053 8|
|hectares||square miles||0.003 861 02|
HERA = Human and Environmental Risk Assessments on ingredients of household cleaning products. A voluntary industry programme to carry out Human and Environmental Risk Assessments on ingredients of household cleaning products. A European partnership established in 1999 between the makers of household cleaning products (AISE) and the chemical industry (Cefic) who supplies the raw materials.
form of predation in which plants or other photosynthetic organisms are consumed by other plant, fungal or animal organisms. Paraziting plants and animals (arthropods or molluscs) consume living plants and other photosysnthetic organisms, these are phytopatogenes or parasitic herbivory. Microbes degrading organic matter of plant origin are saprotrophs.
the higher heating value (HHV;also known as the gross calorific value or gross energy) of a fuel is defined as the amount of heat released by a specified quantity (initially at 25 °C) once it is combusted and the products have returned to a temperature of 25 °C.
The higher heating value takes into account the latent heat of vaporization of water in the combustion products, and is useful in calculating heating values for fuels where condensation of the reaction products is practical (e.g., in a gas-fired boiler used for space heat). In other words, HHV assumes all the water component is in liquid state at the end of combustion (in product of combustion).
highly toxic substances are defined by U.S. OSHA as the following:
- A chemical substance that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
- A chemical substance that has a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each.
- A chemical substance that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each.
In case of the use of highly toxic substances, standard operating procedures (SOP's) for working with each highly toxic material is obligatory! This written procedure must include knowing the physical properties of the material as well as symptoms of exposure and first aid procedures. Never work with highly toxic materials while alone!