Do some more reading it always helps, but is that 4x4x4 feet or metre or inches or what? If its is you have (4x4=16) 16 square feet, you will want a slightly larger fan and carbon filter.
Also if you want top quality weed you will need around 50watts of hps lighting (or equivalent) per square foot, so 50 x 16 = 800, So You WILL need 800w of lighting to get top quality weed.
Either use a smaller space or get around 800w of lights and a good fan and filter, unless you don't really care about quality.
And what did you mean by 'Do you have to have everything sealed off' this question is just down right stupid. People don't like helping when your too lazy to help yourself this question doesn't make sense, you NEED TO READ more. Ok its simple if you don't want your house/apartment smelling then you need a carbon filter which gets air pulled or pushed through it (your choice). Also there is usually a lot of heat generated by lights so people exhaust the air out a window or simply into another room to control temperatures. So to answer your very stupid question, if the ventilation system ( fans, ducting, carbon filters ) isn't sealed and has holes/tears/leaks then there is no point in using them, but thats very self explanatory i don't know why you asked this.
To answer your original question if you spend $10 on a carbon filter it will be basically pointless, invest $60 in a good carbon filter if you actually want to get rid of smell plus it will last longer than a cheap one. Honestly unless you live next to no one get a good carbon filter or you can get caught very easily, you wont be happy if you get in trouble with the law especially if you go to jail cause you saved a whopping $50 infact you wouldnt have saved anything cause i guarantee a $10 carbon filter wont work for shit.
