Chapter VI : The distinctive emblem - Art. 22.
Art. 22. The distinctive flag of the Convention shall be hoisted only over such medical formations and establishments as are entitled to be respected under the Convention and with the consent of the military authorities. In fixed establishments it shall be, and in mobile formations it may be, accompanied by the national flag of the belligerent to whom the formation or establishment belongs.
Nevertheless, medical formations which have fallen into the hands of the enemy, so long as they are in that situation, shall not fly any other flag than that of the Convention.
Belligerents shall take the necessary steps, so far as military exigencies permit, to make clearly visible to the enemy forces, whether land, air or sea, the distinctive emblems indicating medical formations and establishments, in order to avoid the possibility of any offensive action.