What is the ruling on working in the maintenance and air-conditioning of buildings that belong to companies engaged in permissible activities, some of which are subject to اختلاف (difference of opinion) regarding their permissibility (such as circuses), or permissible activities (such as insurance)?

Working for an air conditioning and maintenance company is permissible. However, your assignment by this company to work for a circus and arts company violates this principle. Therefore, it is not permissible for you to install or maintain air conditioning units for buildings designated for unlawful activities. Similarly, you are not permitted to perform the same work for a commercial insurance company. If a servant is keen on pleasing Allah, avoiding His wrath, and trusts in Allah, Allah will provide him with a goodly provision and facilitate for him means of lawful earning. Allah Almighty says: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect. And whoever relies upon Allah - then He is sufficient for him." (At-Talaq: 2-3).