Most power cables will be rated for maximum temperatures between 60°C and 105°C. This temperature refers to the ambient temperature under normal operating conditions. Higher ambient temperatures could contribute to the melting of the insulating material which may cause arcing or fire. Custom power cords may be built to withstand much higher temperatures if needed, but may be more expensive and use different insulation materials. Cables will usually be rated for either flame retardance or fire resistance. Flame retardant means that the cable will not contribute to the spread of a fire, but they are not designed to maintain a functioning circuit in the presence of open flame. A low smoke property can also be added to reduce the amount of toxic fumes released during a fire. If the cable needs to maintain circuit integrity during a fire – in smoke detector wiring for example, then a fire rated cable will be necessary.