What is a recommendation for using equipment with enriched air containing up to 40% oxygen?

Using regular scuba equipment with enriched air that contains up to 40% oxygen is acceptable because most standard dive equipment is designed to handle oxygen concentrations up to this level without any special modifications. While it's important to ensure that the equipment is free from contaminants that can react with higher levels of oxygen, such as oils or greases, standard recreational dive gear can provide safe functionality in enriched air scenarios.

However, divers must also follow good maintenance practices and ensure that the gear is inspected and cleaned properly, especially if it has been previously used with other gas mixes. When using enriched air, typically no significant modifications or specific "special equipment" are required unless the oxygen concentration exceeds 40%, which would necessitate gear rated for higher oxygen levels to ensure safety. This is why relying on regular scuba equipment for up to 40% oxygen is a valid recommendation.