Some things were never meant to fly!...Dangerous goods 

Some aircrafts accidents/incidents are due to dangerous goods. Dangerous goods are defined as articles and substances which pose a significant risk to health or property when transported by air. They include common items such as battery, butane gas, fire-works, ammunition, weed killer, paint, mercury, etc.  The transport of dangerous goods is ruled by "THE I.C.A.O. TECHNICAL INSTRUCTIONS FOR THE SAFE TRANSPORT OF DANGEROUS GOODS BY AIR (Doc. 9284). This document, is the authentic legal source material on the air transport of dangerous goods onboard worldwide aircrafts.

Warning
Passengers failing to comply with these rules not only put themselves and everybody else in danger but may be in breach of applicable laws and subject to legal penalties. Despite the dangerous goods warnings on tickets, timetables, warning notices and posters at ticket sales offices and check-in counters, passengers still carry dangerous goods. We need to be vigilant; for our security.

LIST OF ITEMS PROHIBITED IN CARRY-ON BAGGAGE ON BOARD AIRCRAFT
For the information of the traveling public, Transport Canada is publishing a list of items that are not permitted in carry-on baggage on board aircraft. Screeners retain the right to refuse any additional items they perceive as a possible threat to the security of air travel. For more info, please go to: www.tc.gc.ca/tdg/menu.htm

Dangerous Goods Forbidden for Air Transport
Some dangerous goods are too dangerous to be carried by air, so they are considered forbidden for air transport. As an example security type attaché cases incorporating dangerous goods such as lithium batteries or pyrotechnics are totally forbidden for transport by air.

Dangerous goods acceptable for air transport are dangerous goods which can be carried as CARGO provided they have been properly prepared for carriage. The risk they pose to health, safety and property are reduced to an acceptable level by firstly, limiting the quantity per package and secondly by packing them in such a manner that the package will not fail during formal handling and transportation. The ICAO technical Instructions contain specific instructions for the preparation of dangerous goods for transportation.  Certain dangerous goods have been excepted from the provisions of the regulations when they are either:

• Carried by passengers or crew
• Carried as operator's property when required for the operation.

With certain exception, dangerous goods must not be carried as hand or checked baggage. The following list of excepted dangerous goods applies not just to passengers but to crew and airline staff as well.

• Matches & lighters: Safety matches or a lighter intended for use by an individual. These items must be carried on one's self and are not accepted as carry-on or checked baggage. Lighters containing unabsorbed liquid fuel (other than liquefied gas), lighter fuel and lighter refills are not permitted on one's person nor in checked or carry-on baggage.
• Alcoholic beverages: Alcoholic beverages not exceeding 70% of alcohol by volume, when packed in receptacle of less than 5 Litres. Alcoholic beverages are permitted as carry-on baggage or checked baggage.
• Toilet articles: Non-radioactive medicinal or toilet articles ( including aerosols ) with no subsidiary risk, when the total net quantity of all such articles carried does not exceed 2 kilograms or 2 Litres, and the net quantity of each single article does not exceed 0.5 kilogram or 0.5 Litre: The term "medicinal or toilet articles " is intended to include items such as hair sprays, perfumes, colognes and medicine containing alcohol. These articles are permitted as carry-on baggage, on one's self or as checked baggage.
• Aerosol: Aerosols in division 2.2 ( non-flammable, non-toxic ), with no subsidiary risk, for sporting or home use, are permitted only in checked baggage.
• Hair curlers containing hydrocarbon gas: No more than one per person, provided that the safety cover is securely fitted over the heating element. Hair curlers are permitted as carry-on baggage or checked baggage but not on one's person. These hair curlers must not be used on board the aircraft at any time. Gas refills for such curlers are not permitted in checked or carry-on baggage.
• Thermometers: Small medical or clinical thermometer which contains mercury, for personal use, when in its protective case. They are permitted as carry-on baggage, on one's self or in checked baggage.
• Oxygen /Air cylinders: Small gaseous oxygen or air cylinders required for medical use. They are permitted as carry-on baggage or checked baggage with the required approval of the operator.
• Oxygen generators: Small oxygen generator for personal use. They are permitted only as checked baggage with the approval of the operator.
• Pacemakers: Radioisotopic cardiac pacemakers or other devices, including those powered by lithium batteries, implanted into a person, or radio-pharmaceutical contained within the body of a person as the result of medical treatment.They are not permitted as carry-on or checked baggage.
• Dry ice: Dry ice in quantities not exceeding 2 kilograms per passenger when used to pack perishables in carry-on baggage, provided the package permits the release of carbon dioxide gas. The operator approval is required only for dry ice in checked baggage.
• C02 cylinders: Small carbon dioxide gas cylinders worn by passengers for the operation of mechanical limbs as well as spare cylinders if required to ensure an adequate supply for the duration of the journey. They are permitted as carry-on baggage, on one's self or checked baggage.
• Lifevest: One small carbon dioxide cylinder fitted into a self-inflating lifevest plus one spare cartridge. These items are permitted as carry-on baggage, on one's self or checked baggage with the approval of the operator.
• Ammunition: Securely boxed, cartridge for sporting purposes (in Division 1.4S), in quantities not exceeding 5 kilograms gross weight per passenger for personal use, excluding ammunition with explosive or incendiary projectiles. Allowances for more than one passenger must not be combined into one package. They are only permitted as checked baggage with the approval of the operator.
• Non-spillable battery: Wheelchairs or other battery-powered mobility devices with non-spillable batteries, provided that the battery is disconnected, the battery's terminals are insulated to prevent accidental short circuits and the battery is securely attached to the wheelchair or mobility device. They are permitted only as checked baggage with the approval of the operator.
• Spillable battery: Wheelchair or mobility devices with spillable batteries. They are permitted only as checked baggage with the approval of the operator and the pilot-in-command must be informed of the location.
• Mercurial barometer: A mercurial barometer carried by a representative of a government weather bureau or similar official agency. The barometer must be packed in a strong outer packaging, having a sealed inner liner or a bag of strong leak proof and puncture resistant material impervious to mercury, which will prevent the escape of mercury from the package irrespective of its position. They are permitted only as carry-on baggage with the approval of the operator and the pilot-in-command must be informed of the location.
• Heat producing articles: Heat producing articles such as underwater torches (Diving lamps) and soldering irons. They are permitted only as carry-on baggage with the approval of the operator.