Can it mean that it is not open

• "Ductless" refers to the absence of ducts (channels for air or other substances).
• "Open" refers to something being accessible, not closed off, or having an opening.

These are two different concepts. A system can be ductless and still be open, or it can be ductless and closed. For example, a ductless fume hood is open to the user for placing materials but does not use ducts to vent air.