This may not always be possible and, if it's really affecting you, it might be worth considering another job. Talk to your doctor about changes you can make to your medication to help you. Employers probably can't reject your application just because you have asthma, unless your asthma would make it impossible for you to do the job. We can't be more definite because we don't know yet whether the new Disability Discrimination Act will cover people with asthma. You are more likely to be protected if you have severe asthma.
Tobacco smoke can aggravate asthma symptoms or trigger an attack.
According to a National Asthma Campaign survey, tobacco smoke is a trigger for more than 80 per cent of people with asthma. If people smoke near you at work, the best approach is to explain your situation and rely on their good nature. Ask them to open a window, or smoke at a specified time when you can be in a different area. If you can't convince your colleagues to help, approach your employer. They have a legal responsibility to ensure, as far as reasonably possible, the health, safety and welfare at work of all their employees.