More specialised detectors do not necessarily have a hermetic construction; for example, LHCb covers only the forward (high-pseudorapidity) region, because this corresponds to the phase space region of greatest interest to its physics program.
mˈoːɹ spˈɛʃəlˌaɪzd dɪtˈɛktɚz duːnˌɑːt nˌɛsɪsˈɛɹᵻli hæv ɐ hɜːmˈɛɾɪk kənstɹˈʌkʃən; fɔːɹ ɛɡzˈæmpəl, ˌɛlˌeɪtʃsˌiːbˈiː kˈʌvɚz ˈoʊnli ðə fˈɔːɹwɚd hˈaɪsˌuːdoʊɹɐpˈɪdᵻɾi ɹˈiːdʒən, bɪkˈʌz ðɪs kˌɔːɹɪspˈɑːndz tə ðə fˈeɪz spˈeɪs ɹˈiːdʒən ʌv ɡɹˈeɪɾɪst ˈɪntɹɛst tʊ ɪts fˈɪzɪks pɹˈoʊɡɹæm.