Silane (SiH4) is a colorless gas composed of silicon and hydrogen atoms. It is widely used in industries such as semiconductor and solar cell manufacturing, and in products like adhesives, sealants, and coatings. Understanding its hazardous properties is important due to its reactivity and potential for harm, necessitating careful attention to safety protocols.
Primary Hazard Types of Silane
Silane’s primary dangers are its extreme flammability, pyrophoric nature, and reactivity. It is a pyrophoric gas, meaning it spontaneously ignites when exposed to air, even without an external ignition source. Leaks can cause fires or form explosive mixtures with air, with a lower flammable limit of 1.37 volume percent.
While immediate ignition upon air contact is typical, delayed ignition can occur under specific conditions, potentially leading to vapor cloud explosions or fireballs, especially if the unignited gas is confined. Silane also reacts violently with oxidizers and halogens like bromine and chlorine. It can slowly react with water to form silicon hydroxides and hydrogen gas.
How Silane Affects the Body
Exposure to silane primarily occurs through inhalation, although skin and eye contact are also possible routes. Inhalation can cause irritation to the nose, throat, and lungs, leading to symptoms such as coughing, wheezing, and shortness of breath. High concentrations may result in headache, nausea, and irritation of the mucous membranes and respiratory tract. Prolonged exposure can also lead to central nervous system effects like drowsiness and seizures.
Silane can also act as an asphyxiant by displacing oxygen in the air, especially in poorly ventilated or confined spaces. Skin contact may cause irritation, redness, and itching, while contact with the compressed gas can result in cold burns or frostbite. Eye contact can lead to irritation, redness, pain, and potentially severe damage or frostbite if exposed to the liquid or cold gas.
Safe Handling and Storage Practices
Strict adherence to safety protocols is important when managing silane. It should only be used in well-ventilated areas, ideally with local exhaust ventilation or fume hoods, to prevent gas accumulation. All equipment used with silane must be spark-proof, explosion-proof, and properly grounded to prevent static electricity.
Personal protective equipment (PPE) is necessary for handling silane. This includes flame-resistant clothing (e.g., Nomex suit), fire gloves, safety glasses, and a face shield to protect against fire and splashes. Respirators may be required if ventilation is insufficient. Silane cylinders must be stored in a gas cabinet or exhausted enclosure, away from combustible materials, oxidizing substances, and ignition sources. Cylinders should be secured upright to prevent tipping and stored in a cool, dark, dry area below 125°F (52°C).
Emergency Response and First Aid
In the event of an accidental release or fire involving silane, immediate action is necessary. For a silane gas leak, the area should be evacuated, and all personnel not wearing protective equipment should be removed from the danger zone. Emergency services should be contacted, and personnel should remain at a safe distance to provide information to first responders. If a silane fire occurs, the flow of gas should be stopped if it can be done safely. Attempting to extinguish a silane fire before stopping the gas flow can lead to an accumulation of gas and a subsequent explosion.
For inhalation exposure, move the affected person to fresh air immediately. If breathing has stopped, artificial respiration should be administered, and if breathing is difficult, qualified personnel may provide oxygen. Immediate medical attention is necessary. For skin contact, remove contaminated clothing and flush the affected area with water for at least 15 minutes. For eye contact, flush eyes thoroughly with water for at least 15 minutes, removing contact lenses if present, and seek immediate medical attention. Ingestion is an unlikely route of exposure for silane gas, but if it occurs, seek prompt medical attention and do not induce vomiting.