The invention relates to a method of manufacturing a medical device (1, 299, 399), the method comprising: (i) receiving in a first cleanroom environment categorised by a first airborne particulate cleanliness a plurality of medical components (10, 20, 50, 50′, 210, 220, 320, 350) prepared in a second cleanroom environment categorised by a second airborne particulate cleanliness, which is higher than the first airborne particulate cleanliness, where each of the plurality of medical components (10, 20, 50, 50′, 210, 220, 320, 350) comprises a sealed surface portion, (ii) assembling at least the plurality of medical components (10, 20, 50, 50′, 210, 220, 320, 350) in the first cleanroom environment, thereby providing a sub-assembly, and (iii) establishing an enclosure for the sub-assembly capable of maintaining an internal airborne particulate cleanliness equivalent to the first airborne particulate cleanliness.