def ppd_threshold_from_comfort_class(comf_class):
    """Get acceptable PPD comfort threshold given the EN-15251 comfort class.

    Args:
        comf_class: An integer representing the EN-15251 comfort class.
            Choose from: 1, 2, 3 (the higher the class, the greater the PPD threshold)

    Returns:
        ppd_thresh -- Acceptable PPD threshold.
    """
    if comf_class == 1:
        ppd_thresh = 6
    elif comf_class == 2:
        ppd_thresh = 10
    elif comf_class == 3:
        ppd_thresh = 15
    else:
        raise ValueError(
            'Comfort class {} is not an acceptable value. Choose from: 1, 2, 3'
            .format(comf_class))
    return ppd_thresh
