Plugging one extension cord into another increases length, connections, voltage drop, and opportunities for overload, heating, or damage and is not a recommended way to extend permanent wiring. Use one cord of the correct gauge and length or provide an outlet where power is actually needed.
Use one extension cord with adequate capacity
Check the appliance current or wattage and the cord's marked rating. A longer, thinner cord can heat more; do not try to create capacity by combining strips or extension cords to gain more outlets.
Do not turn extension cords into permanent wiring
A temporary cord should not run under rugs, through doors or walls, or where it is pinched. If the same extension is always needed, the solution is a properly installed receptacle rather than a permanent cord chain.
Every added connection can heat or loosen
Loose plugs, adapters, and connections on the floor are points where resistance and damage can develop. If a plug or receptacle becomes hot, discolored, crackles, or smells burned, stop using it and disconnect from a safe location.
High-power appliances need a more direct solution
Space heaters, portable air conditioners, and other high-load equipment often require direct wall connection according to the manufacturer. Do not use chained extension cords to reach a distant outlet for these loads.
Sources
- U.S. Consumer Product Safety Commission — Electrical Safety — Household electrical-safety guidance and warning signs that call for stopping use or professional help.