Spacers should be used whenever a child is prescribed a metered-dose inhaler, especially if they have difficulty using the inhaler correctly. Specific indications include: - Asthma: To ensure effective delivery of bronchodilators and corticosteroids. - Chronic obstructive pulmonary disease (COPD): Though less common in children, those affected can benefit from spacers. - Acute respiratory conditions: For better administration of rescue medications.