This document presents the protocol for analyzing the short-term effects of air pollution on mortality in Valencia, Spain. The response variables are daily deaths from all non-external causes. Explanatory variables include daily levels of various pollutants (black smoke, SO2, NO2, CO, O3) and possible confounding factors like weather, flu cases, and structural variables. A Poisson regression model is built in two stages: first fitting a baseline model using confounders, then including pollution variables and controlling for autocorrelation. The baseline model fitting process involves including significant terms for various factors like temperature, humidity, time trends, and days of the week.