The primary reason why gas won't ignite is due to a lack of the necessary conditions for combustion. For a flame to ignite, three elements must be present: fuel, an oxidizer (usually oxygen), and a heat source. If any of these elements are missing or insufficient, the gas will not ignite.

The most common reasons for a lack of ignition include:

1. Insufficient oxygen: If the air-fuel mixture is too rich (meaning there is too much fuel and not enough oxygen), the flame will not ignite. This can happen in environments with poor ventilation or when the air filter is clogged.

2. Lack of spark: A spark is required to initiate the combustion process. If the spark plug is not functioning properly or is not producing a strong enough spark, the gas will not ignite.

3. Incorrect fuel pressure: If the fuel pressure is too low, the fuel may not be delivered to the combustion chamber in the correct amount, preventing ignition.

4. Faulty fuel injectors: Clogged or malfunctioning fuel injectors can restrict the flow of fuel, leading to a failure to ignite.

Data from the National Fire Protection Association (NFPA) indicates that a significant number of residential fires are caused by malfunctioning appliances, including those that use gas. For instance, in 2019, there were an estimated 55,620 home structure fires reported in the United States, resulting in 805 civilian deaths, 2,640 civilian injuries, and $1.9 billion in direct property damage. Many of these fires were attributed to issues with gas appliances, highlighting the importance of proper maintenance and operation to prevent ignition failures.