ɹuːbˈɪdiəm ænd sˈiːsiəm mˈʌst biː kˈɛpt ɐwˈeɪ fɹʌm ˈɛɹ, ˈiːvən ˌʌndɚɹ ˈɔɪl, bɪkˈʌz ˈiːvən ɐ smˈɔːl ɐmˈaʊnt ʌv ˈɛɹ dᵻfjˈuːzd ˌɪntʊ ðɪ ˈɔɪl mˈeɪ tɹˈɪɡɚ fɔːɹmˈeɪʃən ʌvðə dˈeɪndʒɚɹəsli ɛksplˈoʊsɪv pəɹˈɑːksaɪd; fɚðə sˈeɪm ɹˈiːzən, pətˈæsiəm ʃˌʊd nˌɑːt biː stˈoːɹd ˌʌndɚɹ ˈɔɪl ɪn ɐn ˈɑːksɪdʒəŋkəntˈeɪnɪŋ ˈætməsfˌɪɹ fɔːɹ lˈɔŋɡɚ ðɐn sˈɪks mˈʌnθs.
Rubidium and caesium must be kept away from air, even under oil, because even a small amount of air diffused into the oil may trigger formation of the dangerously explosive peroxide; for the same reason, potassium should not be stored under oil in an oxygen-containing atmosphere for longer than 6 months.