I made an incubator out of an old cupboard. It has 2 light bulbs to heat it up which is adjusted by a dimmer switch, i have trays of water for the humidity which i regularly fill up with distilled water. I also have a thermometer/humidity clock which informs me to the exact point of what the temperature and humidity is. I have set 3 lots of eggs first time 6 second time 9 and third time 13 i have only had 1 chick hatch and that was from my first batch. In all attempts the chicks have developed but never hatched other than the 1 from my first attempt. The temperature is always between 37.5 degrees Celsius and 39 degrees Celsius which i have read is acceptable. The humidity is around 45%-55% in the first 18 days and i can increase it slightly by spraying water in during the last 3 days which can increase it up to 65%-70% however it may drop back down to the 45%-55% between spraying. I think the ventilation may be too low as there is 1 slot between the 2 doors which open which is 1 inch wide and around 12 inches long, extra ventilation is added when i open the doors to turn the eggs. I am unsure whether this is enough? My worries are increased as my last 13 which i had in started to go rotten and smelt terrible. Even the ones which had chicks in started to smell so in the end around day 19 i through them all because i couldn't stand the smell. My eggs which i use are home produced from my Rhode Island Reds and my cockerel which is an Old English Game. Any help on how to increase the hatching rates would be greatly received before i start my next lot in a few days time.