So what is happening when i keep the temperature to 26?

So what is happening when i keep the temperature at 26? Is it only my family having this problem or even some of you have faced it before? Ok, let me give you the details of the AC. Its 1.5 ton split air-conditioner. And if you are going to say that the AC is not clean and if thats the reason we are getting affected, then you are wrong. Because we clean our AC every month. What else can cause the problem?

Answer: Ventilate the room from time to time; the room size may be small; dusty air is circulated inside.