electrical burn smell

I put as heavy a power burden on the outlet that I thought might be the problem, I ran a fan, light and heating pad...nothing. That has been one of the problems...I haven't been able to predict when the smell will worsen...at times I can't smell it all. It actually started a month ago, suddenly the unit filled with smoke (electrical smell), the alarm when off but I thought maybe the fan had pulled the smell of outside. It has never been that bad since..not even close but occasionally when I open that cabinet, I smell the electrical smell there...but it is not consistent.