Words that end in “-ing” can have different functions in a sentence (different parts of speech).They can be part of a verb to describe an action in the present.

Example:

Be careful while the door is opening.

They can also be adjectives.

Example:

An opening door can be dangerous.

They can be nouns or parts of noun phrases.

Example:
Opening a door can be dangerous
They can be used to make long strings of modifiers, noun phrases, and dependent clauses.

Example:
A mechanic opening a door without obeying the specified safety precautions can easily cause injury to persons standing near the door.

Because these different functions in a sentence can often cause ambiguity or lead to long, complex sentences, it is generally not permitted in STE to use words that end in “-ing.”

Examples:
Non-STE: When you are doing this procedure, obey all the safety precautions.
STE: When you do this procedure, obey all the safety precautions.

Non-STE: Mechanics wearing insufficient protective clothing and opening containers containing hazardous materials in areas where there is a lack of ventilation, using inappropriate tools without observing the manufacturer's instructions, are in danger of coming into contact with these materials and thus suffering from skin irritation and breathing problems.

STE: Before you use dangerous materials, obey these precautions:
- Read the manufacturer's instructions.
- Make sure that there is sufficient airflow in the work area.
- Put on a face mask and protective clothing.
- Get the correct tools to open the containers for these materials.
If you do not obey these precautions, injury to your skin and lungs can occur.

You can use the “-ing” form of a verb only as a modifier in a technical name. This is an adjective which describes the function of a system, component, part, tool or equipment. You can also use it in titles to describe a task, such as “cleaning.”

Examples:

Air conditioning system, grinding wheel, polishing disc, sanding machine, switching relay, welding torch

There are only very few approved words in the dictionary that have an “-ing” ending. They are:
- Adjectives (mating, missing and remaining)
- Nouns (lighting, opening, routing and servicing)
- A preposition (during).