airless / heirless are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
airless: (adjective) lacking fresh air.
heirless: NA
airless: EH·r·l·ah·s
heirless: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)