Concrete can be safely installed in freezing weather if precautions and frost protection equipment are prepared and available before work is stared. Evidence of this is all the successful concreting operations performed in Canada during the winter months. However, if no protection is given to the structure while the concrete hardens, disaster is certain as in the case of the collapse of a eight story hotel building in Michigan in 1924. In this case compressive strengths ranged only from 247 to 781 psi and therefore were not even able to hold up the dead weight. Freezing is also a problem for the grout used in post-tensioning work. One possible solution is to mix alcohol to act as an anti-freeze. Another temperature related effect is the change in dimension buildings experience. In buildings with better control of internal temperatures the range of differences at the roof level increases. Change is size of the roof slab where rigid attachment is made to the walls may result in cracked walls. A possible solution is providing a one inch gap between the face of the roof spandrel and the brick covering. This extra space provided the desired freedom of movement and no cracks formed later on. On the opposite temperature extreme, concrete was once thought to be a fireproofing cover for steel. Yet in 1919, intense fires caused severe damage to five buildings. It was found that cinder concrete was little value if all of the unburnt coal was not removed. Gravel concrete was of less value than crushed stone mix since the gravel normally has different coefficients of expansion along different axes and under intense heat will pop out of the concrete. Related to this are fires caused by frost protection equipment. In this case, a fire broke out in New York when a propane tank blew up and the resulting fire consumed the forms and destroyed two floors 30 feet above the street.