Frequently Asked Questions:

1. What are peroxides and why are they perilous?
2. Common peroxide-forming chemicals and reagents.
3. What should I know about storing organic peroxide?
4. What should I be aware of in the organic peroxide storage area?
5. What should I know about organic peroxide storage temperatures?
6. What is important to know about dispensing or transferring organic peroxides?
7. What is important to know when handling organic peroxides?
8. How should I dispose of organic peroxides?
9. Why is good housekeeping important?
10. Why is personal cleanliness important?
11. Why is equipment maintenance important?
12. What should I know about Personal Protective Equipment and organic peroxides?
13. How should I handle emergencies?
14. What are basic safe practices concerning organic peroxides?
15. What are ignition sources?
16. What is spontaneous combustion?
17. What should a good storage area be like?
18. Why is venting of flammable liquid drums important?
19. Why should I label containers?
20. How do I dispense flammable and combustible liquids carefully?
21. How do I dispose of waste material safely?

1. What are peroxides and why are they perilous?

Organic peroxides are carbon-based chemicals that include a double oxygen (-O-O-) bond in their molecular structure. This double-oxygen bond contributes to the chemical instability of organic peroxides because it can readily decompose, yielding heat, flammable vapors, fire, or explosion. This potentially hazardous decomposition can be triggered by heat, shock, friction, and contamination with incompatible substances.

How hazardous is this decomposition? Russian authorities have acknowledged that the fire and explosion that sank the submarine Kursk was caused by the violent decomposition of highly concentrated hydrogen peroxide leaking from one of the ship's torpedoes. The initial explosion and fire in turn caused the remaining torpedoes to simultaneously explode about 2 minutes later, sealing the ship's fate. 

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2. Common peroxide-forming chemicals and reagents.

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3. What should I know about storing organic peroxide?

Before storing, inspect all incoming containers to ensure that they are undamaged and properly labelled. Do not accept delivery of defective containers.

Store organic peroxides in the containers that the chemical supplier recommends. Normally, these are the same containers in which the material was shipped. Repackaging can be very dangerous, especially when using contaminated or incompatible containers.

Make sure containers are suitably labelled. For organic peroxides requiring temperature control, the recommended storage temperature range should be plainly marked on the container. It is also a good practice to mark the date that the container was received and the date it was first opened.

Protect containers against impact or other physical damage, when storing, transferring or using them. Do not use combustible pallets, such as wood, for storing organic peroxide containers.

Normally, keep containers tightly closed to avoid contamination in storage except when the supplier's instructions state otherwise.

Storing open or partly open containers of peroxides diluted with solvents, including water, can lead to evaporation of the solvent. This can expose the more hazardous dry peroxide.

Some liquid organic peroxides, however, such as methyl ethyl ketone peroxide, gradually decompose giving off gas. These peroxides are shipped in containers with specially vented caps. Use no other type of cap for containers of these organic peroxides. The vent caps relieve the normal buildup of gas pressure that could shatter an unvented container. Check vent caps regularly to ensure that they are working properly. Keep vented containers in an upright position. NEVER stack vented containers on top of each other.

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4. What should I be aware of in the organic peroxide storage area?

Store organic peroxides separately, away from processing and handling areas. Keep them away from incompatible materials such as strong acids and bases, other oxidizing materials, flammable or combustible liquids and materials that can be oxidized (often called reducing materials or agents). Separate storage can reduce personal injury and damage caused in case of fires, spills or leaks.

Check the reactivity data and storage requirements sections of the MSDS for details about what materials are incompatible with a specific organic peroxide.

Construct walls, floors, shelves and fittings in storage areas from noncombustible materials that are compatible with the organic peroxides.

Ensure that floors are resistant to penetration by the organic peroxides in storage. Floors should have no cracks in which chemicals could lodge if spilled.

Since liquid organic peroxides flow easily, provide dikes around large liquid storage areas and sills or ramps at door openings. Store smaller amounts in trays made from compatible materials to contain spills or leaks.

Store containers at a convenient height for handling, below eye level if possible, to reduce the risk of dropping them. Avoid overcrowding in storage areas. Do not store containers in out-of-the-way locations where they could be forgotten.

Store containers away from doors. Although it is convenient to place frequently used materials next to the door, they could cut off the escape route if an emergency occurs.

Store organic peroxides in areas which are:

·               Well ventilated

·               Dry, cool, out of direct sunlight and away from steam pipes, boilers or other heat sources

·               Supplied with adequate firefighting equipment, including sprinklers

·               Supplied with suitable spill clean-up equipment and materials

·              Free of ignition sources such as open flames, hot surfaces, burning tobacco and spark-producing tools and devices

·               Accessible at all times

·              Labelled with suitable warning signs

At all times:

·               Allow only trained, authorized people into storage areas.

·               Keep the amount of organic peroxides in storage as small as possible.

·          Inspect storage areas regularly for any deficiencies including damaged or leaking containers and poor housekeeping.

• Correct all deficiencies as soon as possible.

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5. What should I know about organic peroxide storage temperatures?

Follow the chemical supplier's recommendations for maximum and minimum temperatures for storage and use. Higher temperatures can be hazardous since they speed up the decomposition rate of organic peroxides. Where appropriate, keep the maximum storage temperature less than 38°C (100°F).

Some organic peroxides must be kept at low temperatures in refrigerators or freezers. Use only approved or specially modified units (generally known as "laboratory safe"). Standard kitchen refrigerators and freezers contain many ignition sources inside the cabinet. If the storage area requires explosion-proof equipment, keep the refrigeration unit and all electrical equipment outside the area. Make connections between the refrigerator cabinet and the other equipment using tubing that passes through the wall of the storage area.

Locate refrigeration equipment in a well-ventilated area. This is needed to carry away peroxide decomposition products that might result from a refrigeration failure.

It can be hazardous to store organic peroxides below the minimum recommended temperatures. For example, acetyl peroxide, which is very shock-sensitive, is usually sold as a 25 percent solution in dimethyl phthalate to make it less sensitive. At temperatures below about -8°C (17°F), pure crystals of shock-sensitive acetyl peroxide form. Do not store organic peroxides which are diluted with water at temperatures below 0°C (32°F) to avoid separating out the pure organic peroxide.

Storage areas may need alarms that indicate when storage temperatures are higher or lower than required.

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6. What is important to know about dispensing or transferring organic peroxides?

Open and dispense containers of organic peroxides in a special room or area outside the storage area. Do not allow any ignition sources in the vicinity. Take care that the organic peroxides do not contact combustible or other incompatible materials when they are dispensed.

Use containers and dispensing equipment such as drum pumps, scoops or spatulas that the chemical supplier recommends. These items must be made from non-sparking materials compatible with the peroxides used. Keep them very clean to avoid contamination.

When transferring organic peroxides from one container to another, avoid spilling or contaminating your skin or clothing. Spills from open, unstable or breakable containers during material transfer have caused serious accidents.

Never transfer liquids by pressurizing their usual shipping containers with air or inert gas. The pressure may damage ordinary drums and barrels. Moreover, if air is used, it may create a flammable atmosphere inside the container.

Glass containers with screw-cap lids or glass stoppers may not be acceptable for some organic peroxides, especially those sensitive to friction and grinding. Never transfer materials stored in a vented container into a tightly sealed, non-vented container. The buildup of gas pressure could rupture it. Dispense from only one container at a time. Finish all the dispensing of one material before starting to dispense another. Dispense the smallest amount possible, preferably only enough for immediate use. Keep containers closed after dispensing, to reduce the risk of contaminating their contents.

Never return unused material, even if it does not seem to be contaminated, to the original container.

If a water-based formulation freezes, do not chip or grind it to break up lumps of material, or heat it to thaw it out. Follow the chemical supplier's advice.

Avoid dropping, sliding or skidding heavy metal containers such as drums or barrels of friction- or shock-sensitive material.

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7. What is important to know when handling organic peroxides?

Make sure that all areas where organic peroxides are used are clean and free of combustible and other incompatible materials and any ignition sources. Temperatures in peroxide use areas should be controlled so as to not become high enough to cause rapid decomposition.

Diluting Organic Peroxides

Some jobs require diluting organic peroxides prior to use. Do this strictly according to the chemical supplier's advice. Using the wrong solvent or a contaminated solvent could cause an explosion. For example, methyl ethyl ketone peroxide and cyclohexanone peroxide may explode if they are mixed with acetone, a common solvent. Using reclaimed solvents of uncertain composition can also be hazardous. They may contain dangerous concentrations of contaminants that are incompatible with the organic peroxide.

Hazardous Operations

Some operations involving organic peroxides can be especially hazardous. Accidents have occurred during distillation, extraction or crystallization, because these processes concentrated the organic peroxides. Filtering friction- or shock-sensitive chemicals with materials and devices that produce heat, such as sintered glass filters, can be hazardous.

Before using a new material in an operation, find out as much as possible about the potential hazards of the particular peroxide and operation.

Using Organic Peroxides with Resins

Organic peroxides are often used as catalysts to activate resins in plastics production. Never mix organic peroxides directly with any accelerators or promoters. A violent explosion may result. Thoroughly mix the accelerator or promoter in the resin mixture before adding the organic peroxide.

It is dangerous to dissolve peroxides in very small amounts of monomer (such as styrene) before adding them to the resin mixture. These "small quantity" mixtures can undergo rapid polymerization giving off a lot of heat. This may result in a fire.

Regular workplace inspections can help to spot situations in which organic peroxides are stored, handled or used in potentially hazardous ways.

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8. How should I dispose of organic peroxides?

Organic peroxide wastes are hazardous. Dispose of unwanted or contaminated organic peroxides promptly using a method the chemical supplier recommends. Consider organic peroxides accidentally mixed with an unknown or foreign material as contaminated. Never attempt to salvage spilled or contaminated organic peroxides.

Dispose of unused peroxide-resin mixes also. Allow partly cured wastes to set and cool in safe, open areas. Doing this helps to prevent the heat produced during the curing reaction from starting a fire in waste containers.

"Empty" drums, bottles, bags and other containers usually contain hazardous residues. Never use these containers for anything else, no matter how clean they seem. Treat them as organic peroxide wastes. Follow the chemical supplier's advice about how to safely handle or decontaminate "empty" containers.

Store organic peroxide waste in the same way as unused organic peroxides. Use only compatible containers for wastes. Identify their contents with suitable labels.

Never dispose of organic peroxides in ordinary garbage or down sinks or drains that connect to sanitary or storm sewers. Dispose of them according to the supplier's advice, or through hazardous waste collection and disposal companies. In all cases, dispose of organic peroxide wastes according to the environmental laws that apply to your jurisdiction. Contact the appropriate environmental officials for details.

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9. Why is good housekeeping important?

Maintain good housekeeping at all times in the workplace:

·               Clean-up any spills promptly and safely according to directions in the MSDS.

·               Be careful not to contaminate anything that can burn. A serious fire resulted when the same cotton rag was used to clean up both spilled organic peroxide and accelerator.

·               Do not use sawdust or other burnable sweeping compounds to clean up organic peroxide spills.

·               Properly dispose of unlabelled or contaminated materials containing peroxides.

·               Promptly remove combustible wastes, including wood, paper and rags, from work areas.

·               Avoid any build-up of organic peroxide dusts on ledges or other surfaces.

·               Ensure that all containers for waste are compatible with the organic peroxides used, properly marked and located close to the job.

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10. Why is personal cleanliness important?

Personal cleanliness helps protect you when you are working with organic peroxides:

·               Wash hands before eating, drinking, smoking or going to the toilet.

·               Remove contaminated clothing and footwear, since they can be a severe fire hazard.

·               Wash contaminated items immediately and thoroughly in water before re-wearing or discarding.

·               Do not wear or carry contaminated items into areas having ignition sources or where smoking is allowed.

·               Store food and tobacco products in uncontaminated areas.

·               Avoid touching yourself with contaminated hands.

·               Wash thoroughly at the end of the workday.

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11. Why is equipment maintenance important?

Regular equipment maintenance can prevent leaks or emissions of organic peroxides into the workplace:

·               Ensure that maintenance personnel know the possible hazards of the materials they may encounter and any special procedures and precautions needed before they begin work.

·               Prevent leaks of grease or other lubricants from equipment where organic peroxides are used.

·               Do not allow materials such as cleaning solvents, paints or thinners to contact organic peroxides.

·               Be very careful when cutting, welding or doing other hot work on organic peroxide containers or equipment.

·               Comply with applicable regulations and contact the chemical supplier for advice.

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12. What should I know about Personal Protective Equipment and organic peroxides?

If other methods, such as engineering controls, are not available or effective in controlling exposure to organic peroxides, wear suitable personal protective equipment (PPE). Choosing the right PPE for a particular job is essential. MSDSs should provide general guidance. Also obtain help from someone who knows how to evaluate the hazards of a specific job and how to select the proper PPE.

Avoid Skin Contact

When using materials that are harmful by skin contact, wear protective gloves, aprons, boots, hoods or other clothing, depending on the risk of skin contact. Choose clothing made of materials that resist penetration or damage by the chemical. The MSDS should recommend appropriate materials. If it does not, contact the chemical supplier for specific information.

Protect Your Eyes and Face

Always wear eye protection when working with organic peroxides. Avoid ordinary safety glasses. Use chemical safety goggles instead. In some cases, you should also wear a face shield to protect your face from splashes. The current Canadian Standards Association (CSA) Standard Z94.3, "Industrial Eye and Face Protectors," provides advice on selection and use of eye and face protectors.

Avoid Breathing Dust, Vapours or Mists

If respirators must be used for breathing protection, there should be a written respiratory protection program to follow. Guidance for developing a program can be found in the current CSA Standard Z94.4, "Selection, Care, and Use of Respirators." Follow all legal requirements for respirator use and approvals. These may vary between jurisdictions in Canada.

Sorbents in respirator cartridges or canisters must be compatible with the chemical they are supposed to protect against. For example, oxidizable sorbents, such as activated charcoal, may not be acceptable if high airborne concentrations of organic peroxides are present. A hazardous reaction might occur. Know and be familiar with the right PPE for emergencies, as well as normal operations.

Wear the PPE needed for doing a particular job. It cannot provide protection if it is not worn.

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13. How should I handle emergencies?

Act fast in emergencies like chemical fires, spills and leaks.

·               Evacuate the area at once if you are not trained to handle the problem or if it is clearly beyond your control.

·               Alert other people in the area to the emergency.

·               Call the fire department immediately.

·               Report the problem to the people responsible for handling emergencies where you work.

·               Obtain first aid if you have been exposed to harmful chemicals and remove all contaminated clothes.

Check that emergency eyewash stations and safety showers are available wherever accidental exposure to organic peroxides that can damage skin or eyes might occur.

Only specially trained and properly equipped people should handle emergencies. Nobody else should go near the area until it is declared safe.

Planning, training and practicing for emergencies help people to know what they must do. Prepare a written emergency plan. Update it whenever conditions in the workplace change.

The MSDSs for the materials used are a starting point for drawing up an emergency plan. MSDSs have specific sections on spill clean-up procedures, first aid instructions, and fire and explosion hazards including suitable fire extinguishing equipment and methods. If the directions in each MSDS section are unclear or seem incomplete, contact the material's supplier for help.

It is very important to know the best ways to fight fires involving organic peroxides. The "built-in" supply of oxidizing gas in organic peroxides makes extinguishing methods based on smothering ineffective (for example, foam or carbon dioxide). Often, cooling with large amounts of water is the only suitable method.

Many other sources can also help develop emergency plans. Local fire departments can assist with fire emergency plans and training. Occupational health and safety and environmental enforcement agencies, provincial safety associations, St. John Ambulance, insurance carriers, professional societies in occupational health and safety, labour unions, trade associations, some local colleges and universities and CCOHS can supply useful information at little or no cost. Specialized private consultants are also available.

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14. What are basic safe practices concerning organic peroxides?

Following these basic safe practices will help protect you from the hazards of organic peroxides:

·               Read the Material Safety Data Sheets (MSDSs) for all of the materials used in your work.

·               Know all of the hazards (fire/explosion, health, corrosivity, chemical reactivity) of the materials used in your work.

·               Know which of the materials you work with are organic peroxides.

·               Store organic peroxides in suitable, labelled containers (usually their shipping containers) in a cool, dry area.

·               Inspect containers for damage or leaks before handling them.

·               Store, handle and use organic peroxides in well-ventilated areas and away from incompatible materials.

·               Follow the chemical supplier's advice about maximum and minimum storage and use temperatures.

·               Eliminate ignition sources (sparks, smoking, flames, hot surfaces) when working with organic peroxides.

·               Handle containers safely to avoid damaging them.

·               Keep containers closed when not in use.

·               Keep only the smallest amounts possible (not more than one day's supply) in the work area.

·               Dispense organic peroxides carefully, using compatible equipment, into acceptable containers.

·               Do not grind or subject organic peroxides to any type of friction or impact.

·               Be careful when performing operations such as distillations or separations that concentrate organic peroxides.

·               Never return unused or contaminated organic peroxides to their original containers.

·               Return unopened containers to the proper storage area and opened containers to a dispensing or premixing area at the end of the day.

·               Practice good housekeeping, personal cleanliness and equipment maintenance.

·               Handle and dispose of organic peroxide wastes safely.

·               Wear the proper personal protective equipment for each of the jobs you do.

·               Know how to handle emergencies (fires, spills, personal injury) involving the organic peroxides you work with.

·               Follow the health and safety rules that apply to your job.

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15. What are ignition sources?

For a flammable or combustible liquid fire to start, a mixture of vapour and air must be ignited. There are many possible ignition sources:

·               Sparks from electrical tools and equipment.

·               Sparks, arcs and hot metal surfaces from welding and cutting.

·               Tobacco smoking.

·               Open flames from portable torches and heating units, boilers, pilot lights, ovens, and driers.

·               Hot surfaces such as boilers, furnaces, steam pipes, electric lamps, hot plates, irons, hot ducts and flues, electric coils and hot bearings.

·               Embers and sparks from incinerators, foundry cupolas, fireboxes and furnaces.

·               Sparks from grinding and crushing operations.

·               Sparks caused by static electricity from rotating belts, mixing operations or improper transfer of flammable or hot combustible liquids.

You can eliminate many of these ignition sources by:

·               Removing open flames and spark-producing equipment.

·               Not smoking around these liquids.

·               Using approved explosion-proof equipment in hazardous areas.

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16. What is spontaneous combustion?

Spontaneous combustion occurs when a material in contact with air can heat up sufficiently (without an outside heat source) to burn. The oils in some wastes and rubbish can slowly react with oxygen in the air. This reaction creates heat that can build up over time if the wastes are left undisturbed. When the heat level in a "self-heating material" is high enough (i.e., when the temperature reaches the autoignition temperature), a fire may start.

For example, rag soaked with vegetable oil in the bottom of a pail could heat up enough to cause spontaneous combustion of the rag. However, the same oil-soaked rag would not be expected to heat up on a clothes line because there would sufficient contact with moving air that would prevent heat from building up. An oil-soaked rag would not heat up if it were in a tight bale because it would not have enough air. Similarly, wet or improperly cured hay stored loose (i.e., not baled) in a barn is susceptible to heating up enough to cause spontaneous combustion. In the cases of spontaneous combustion of hay, grain and oil seeds, the source of heat comes from the action of microorganisms (e.g., bacteria, fungi) on materials having the right moisture and temperature conditions. Damp charcoal, meals (i.e., ground seeds), materials (fabrics, rags, cotton, etc.) soaked with paints containing drying oils are some other examples of materials have a spontaneous combustion hazard.

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17. What should a good storage area be like?

Store flammable and combustible liquids in areas that are:

·               well ventilated to reduce vapour concentrations.

·               free of ignition sources.

·               cool (temperature controlled) and dry.

·               supplied with adequate firefighting and spill clean-up equipment.

·               away from elevators, building and room exits, or main aisles leading to exits.

·               accessible by firefighters.

·               labelled with suitable warning signs. For example: "No Smoking".

Avoid storing flammable and combustible liquids in basements. Ground floor storage is usually preferred as it provides easier access for emergency situations.

Inspect storage areas regularly for any deficiencies such as damaged or leaking containers, poor ventilation or non-approved equipment. Unapproved modifications or damage to approved or explosion-proof equipment or systems could result in unintended hazardous conditions. Correct all deficiencies as soon as possible.

It may be possible to store small amounts of flammable liquids (less than 235 litres or about 62 U.S. gallons) and combustible liquids (less than 470 litres or about 124 U.S. gallons) in approved containers in specially designed storage cabinets near their point of use.

Volatile, flammable liquids are sometimes stored in refrigerators. Use specially designed and approved refrigerators (generally described as "laboratory safe") for this. Standard domestic refrigerators contain many ignition sources and should not be used for storing flammable solvents.

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18. Why is venting of flammable liquid drums important?

Drums of flammable liquids should have pressure- and vacuum-relief venting installed. Normally, this is done as soon as the drum is opened for dispensing. If a stored drum will be exposed to heat sources or large temperature changes, relief venting may be needed.

Storing a full drum in direct sunlight or near other heat sources can increase vapour levels in the drum. This leads to an increase in pressure that could, in extreme cases, cause the drum to rupture. A buildup in pressure can also result in vapour shooting out into the face or onto the clothing of the person opening the drum. A pressure-relief vent prevents this increase in pressure.

Vacuum-relief vents are also useful. If a drum of flammable liquid is subjected to sudden cooling, a partial vacuum can form inside it. This could, in extreme cases, cause the drum to collapse and leak. Also, for proper dispensing of liquids, the space left behind by the liquid in the drum must be replaced with air so that no vacuum forms. There are different kinds of pressure-relief and vacuum-relief devices, including combination types, available from safety equipment retailers.

Safety Cans

Portable safety cans for carrying, storing and dispensing flammable and combustible liquids are widely used. They are available in different shapes and in capacities from 0.5 to 25 litres. Approved safety cans are made from metal or very low conductivity plastic. Safety cans have spring-mounted spout caps. These automatically open when the vapour pressure builds up inside, to allow vapours to escape and prevent rupture (or explosion, in the event of fire). The cap-operating mechanisms also cause the spout cap to close automatically when you finish filling or pouring from the safety can, or if the can is dropped.

This safety feature could create a hazard under some conditions. In a warm enclosed space, such as a car trunk, vapours venting from a safety can might reach flammable levels. A spark could cause an explosion. For temporary transport of small amounts (normally less than 25 litres) of flammable liquid, use an approved pressure-resistant and non-venting container. Eliminate ignition sources and ensure good ventilation, too.

Safety cans may also have wire mesh flame arrester screens inside the cap spouts. These prevent flashbacks from reaching the liquid in the cans.

Other Approved Containers

Other types of approved containers include:

·               Rinse and cleaning tanks for dipping or washing parts in liquid.

·               Plunger cans for moistening cleaning rags.

·               Bench cans for dipping and rinsing small parts.

·               Dispenser or "benzine" cans for dispensing small amounts of liquid directly on work or cloths.

·               Containers for disposal of flammable and combustible liquids and oily rags and waste.

These approved safety containers also have different kinds of safety devices, such as self-closing lids or flame arresters. Containers like some rinse or dip tanks, or oily rag and waste cans with lids that are not self-closing are held open by fusible link devices. In the event of a fire in an open container, the fusible link melts, closing the lid and smothering the fire.

In certain cases, flammable and combustible liquids may be stored, handled and used in approved, non-reusable glass or plastic containers (usually the ones they are shipped in), holding no more than 5 L. This may be acceptable if the required liquid purity (such as analytical reagent grade or higher) is affected by storage in metal containers, or if the liquid causes excessive corrosion of metal containers.

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19. Why should I label containers?

Properly label all containers used for flammable and combustible liquids. This helps prevent accidentally mixing one chemical with another and reduces the chances of mistaking one liquid for another. Plainly mark the name of the liquid and its hazard on the container. Keep the label clean so that it can be easily seen at all times. Never use a container for any liquid except the one that is marked on the label.

Using unsuitable containers such as jam jars, saucers, open cans, buckets or pails is a dangerous practice. Open containers allow hazardous vapours to escape. Breakable containers increase the chance of serious spills.

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20. How do I dispense flammable and combustible liquids carefully?

Take care when dispensing or transferring flammable and combustible liquids from one container to another. Dispense from only one container at a time. Finish dispensing one material before starting to dispense another. Be sure containers are closed after dispensing to control hazardous vapours and to avoid accidental spills. Approved transfer pumps and drum faucets that cannot be left running accidentally are available. Check these devices periodically to be sure that they work properly and do not leak.

Use an approved safety drip can below each drum faucet to catch spills or drips from worn or damaged faucets.

Never dispense flammable and combustible liquids near ignition sources. Always make sure that metal containers are bonded and grounded when dispensing.

Never transfer liquids by pressurizing their usual shipping containers with air. The pressure may damage ordinary drums and barrels, or create a flammable atmosphere inside the containers.

Mark dispensing areas with suitable warning signs.

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21. How do I dispose of waste material safely?

Store waste flammable and combustible liquids in the same way as unused flammable and combustible liquids. Clean drums made of compatible material can be used to store waste liquids if they are vented, grounded and bonded similarly to dispensing drums. Approved safety disposal cans are also available for waste liquids.

Place cloth, paper and other solid materials that are soaked with flammable and combustible liquids in approved oily waste disposal cans. These are made of metal and have self-closing lids. Do not overfill them, and empty them at least at the end of every workday to reduce the chance of spontaneous combustion.

Clearly label all waste containers with their contents.

Be careful with "empty" flammable and combustible liquid containers. They may contain enough liquid to create an explosion hazard. Only about 14 ml (0.5 fluid ounce) of liquid are needed to give enough vapour to form an explosive atmosphere in a 182-litre (40-gallon) drum. This amount can easily be trapped in a seam or be present as a very thin film on the inner surface of the drum. Do not perform any work (welding, cutting, drilling, soldering) on an "empty" liquid container until all liquid and vapours have been cleaned out. Contact the chemical manufacturer or supplier for the best way to do this.

Never pour waste flammable liquids down sinks or drains. Dispose of them through hazardous waste collection and disposal companies. Dispose of these wastes according to the environmental laws that apply to your jurisdiction. Contact the appropriate environmental officials for advice.

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