9 Safety signs and safety advice

There are several ways of giving instructions and advice in safety signs and notices.

No + -ing or noun

This is a direct command to the public, and is found on signs in a range of general and industrial contexts. No smoking No admittance

Imperative

This type of command is not as strict as no + -ing, and can be found in more informal signs, or in safety handbooks.

Positive Wear a safety helmet.

= infinitive Negative Do not smoke here.

= Do not + infinitive

The short form of Do not is Don't. This is used commonly in spoken English and in more informal advice or commands. Don't keep your mobile phone switched on.

We can use always and never to make a command stronger. In a positive command, always comes just before the verb.

Always check the filters.

In a negative sentence, never replaces do not / don't. Never operate the chainsaw without ear protection.

120 Grammar reference

must

Must expresses a strong obligation, and authority, and is used in both the Active and Passive. Remember that must does not change in the he/she / it forms.

Active form

You must wear a safety

helmet. Unauthorized persons must not use this machine.

= subject + must (not) + infinitive Passive form

Eye protection must be worn.

Fire extinguishers must not be used in this area.

= subject + must (not) + be + past participle

We can also use always and never with must. In both the Active and Passive, always and never follow must.

You must always wear a hard hat when work is going on

overhead.

Personnel must never leave this equipment switched on.

High visibility clothing must always be worn in this

area.

Chemicals must never be stored near open flames.

10 Relative clauses

We use a relative clause as a means of joining two pieces of information together within one sentence.

The Ultracane is a device. This device helps blind people.

Relative clause: The Ultracane is a device which helps blind people.

A cardiac patient is a person.

The person is being treated for a heart problem.

Relative clause: A cardiac patient is a person who is being treated for a heart problem.

In relative clauses, we use the relative pronouns who when the subject is a person, or which when the subject is an object.

Note that the subject of who and which can be singular or plural.

Ultracanes are devices which help blind people. Cardiac patients are people who are being treated for heart problems.

There are two types of relative clause: defining and non-defining.

Defining relative clause

This tells us information about an object or person that identifies them.

This is a scanner which reads books. (= there are several types of scanner, and this is one that reads books)

There's the lab technician who works in the laboratory with me. (= there are several lab technicians, and he / she is the one that works with me)

Non-defining relative clause

This tells us supplementary information about an object or person. The relative pronoun who or which is always preceded by a comma.

This is a scanner, which reads books. (= there is only one type of scanner, and it happens to read books)

There's the lab technician, who works in the laboratory with me. {= there is only one lab technician, and he / she works with me)