What must be followed to ensure effective disinfection when using chemical solutions?

The correct answer highlights the importance of adhering to the manufacturer's recommendations when using chemical solutions for disinfection. This is crucial because manufacturers provide specific guidelines based on extensive research and testing that ensure the product is used safely and effectively. These recommendations typically include information on dilution ratios, application methods, contact time, and types of surfaces suitable for the solution.

Following these guidelines ensures that the disinfectant achieves its intended efficacy in eliminating pathogens without causing harm to clients or damaging surfaces and equipment. Moreover, compliance with manufacturer recommendations is often required to maintain professional standards and liability protections within esthetics practices.

Other options do not provide the necessary reliability that comes from standardized guidelines. Personal discretion and common sense practices can vary widely between individuals and may not adhere to safety protocols. Relying on guidelines from friends can lead to inconsistent and potentially unsafe practices, diverting from the structured advice that comes from manufacturers who have developed the products specifically for safe and effective use.