.icon-wrap { display: flex; align-items: center; }
.icon { width: 22px; position: relative; display: inline-block; vertical-align: middle; }
.icon::before { width: 100%; padding-top: 100%; background-size: 100% auto; background-position: center center; background-repeat: no-repeat; display: block; content: '';  }

.icn-pdf::before { background-image: url(../img/icons/icn-pdf.png); }
.icn-pdf2::before { background-image: url(../img/icons/icn-pdf2.png); }
.icn-pc::before { background-image: url(../img/icons/icn-pc.png); }
.icn-pc::before { background-image: url(../img/icons/icn-pc.png); }
.icn-plane::before { background-image: url(../img/icons/icn-plane.png); }