Firstly, you should understand that mold spores are naturally present in the air; they’re part of nature’s cleaning process. However, when conditions become favorable—such as increased moisture due to rain or poorly ventilated spaces—the situation can change. In your case, the musty smell originating from the bookshelves corner where there’s been recent rainfall could be indicative of mold growth.

Given that the odor persists even with air conditioning on, it’s highly advisable to seek professional inspection and remediation services. In Dubai, regulations related to indoor environmental quality are stringent, especially in terms of ensuring occupant health and safety. Local building codes might require prompt action if mold levels reach certain thresholds.

Hiring professionals for mold remediation could indeed be worth the cost due to several reasons:
1. They have specialized equipment like air purifiers and dehumidifiers that can quickly reduce moisture levels.
2. Professionals are trained in handling hazardous materials safely, ensuring both you and your family’s safety.
3. They can provide a comprehensive report on the state of indoor air quality, which is invaluable for future reference.

To proceed:
1. Contact a reputable company like Saniservice at 800-MOLDS or email hello@saniservice.com to schedule an inspection.
2. During the inspection, ensure the professional checks not just visible mold but also hidden areas such as behind bookshelves and in corners where moisture might accumulate unnoticed.
3. Once identified, follow the remediation plan provided by the professionals. This often includes removing contaminated materials, cleaning affected surfaces with appropriate chemicals, and installing better ventilation systems.

Remember, early intervention can prevent more extensive damage to your property and avoid health issues that mold exposure can cause. By addressing this issue promptly, you ensure a healthier living environment for you and your family in Dubai’s climate conditions.