A bar chart displays the volume percentages of gases in dry air at sea level, with nitrogen and oxygen dominating, while trace gases like ozone and xenon appear at minuscule scales. The visualization uses D3 v3 to create an ordinal x-axis and linear y-axis, with hover tooltips showing each gas’s percentage and parts-per-million conversion. Data is loaded from a CSV file via `d3.csv`, and the chart responds to window dimensions, rotating x-axis labels on smaller screens.