Set up your own OpenAI key, with a spending limit

Three things are worth knowing, because they are where most people get stuck:

• OpenAI's developer site is not ChatGPT. You can sign in with the same login, but it has its own billing. Paying for ChatGPT Plus or Pro does not give you any API credit.
• You pay OpenAI, not us. Your DampApp Pro subscription does not include OpenAI's charges. They bill your card directly for what you use.
• A key only works once there is credit on the account. OpenAI is pay-as-you-go with credit bought in advance. With no credit, the AI tools stop with a “quota” message.

1. 1

   Step 1: Create your OpenAI developer account

   Open OpenAI's developer site and choose “Sign up”, or “Log in” if you already use ChatGPT (the same email and password work).

   Open platform.openai.com (opens in a new tab)

   OpenAI may ask you to confirm your email address and phone number, and to name your organisation. Your own name or your company name is fine.

2. 2

   Step 2: Add prepaid credit

   Open the Billing page, add a payment card, then choose “Buy credits” or “Add to credit balance” (OpenAI shows one or the other).

   Open the Billing page (opens in a new tab)

   • The smallest amount you can buy is US$5. OpenAI's default is $10, which lasts most surveyors a long time.
   • Credit expires one year after you buy it, so there is no benefit in buying a lot up front.
   • Allow a few minutes after paying for the balance to show before you try the AI tools.
3. 3

   Step 3: Switch off auto recharge

   OpenAI turns “Auto recharge” on by default while you set up billing. It quietly buys more credit on your card whenever your balance runs low.

   On the same Billing page, find “Auto recharge” and turn it off. Your prepaid balance then becomes the most you can spend. You can always top up by hand later.

   Prefer to leave it on?

   That is fine for heavy users who never want the AI to stop mid-survey. If you do, make sure you also complete step 4, because OpenAI says a recharge limit is not a spending limit.

4. 4

   Step 4: Set a hard monthly spending limit

   This is your safety net. Open the Limits page and, in the “Spend” section:

   Open the Limits page (opens in a new tab)

   1. Select “Edit spend limit”.
   2. Type a “Monthly spend limit”, for example 10 (US dollars).
   3. Turn on “Enforce a hard limit”. This is the important bit. Without it, the limit only sends you an email and the AI keeps running.
   4. Select “Save”.

   OpenAI says its limits are not instant, so spending can go very slightly over the figure you set. When the limit is reached, the AI tools stop until the next calendar month or until you raise it.

5. 5

   Step 5: Create your secret key

   Tip: do this step on the phone or tablet you survey with, so you can copy the key and paste it straight into the app.

   Open the API keys page (opens in a new tab)

   1. Select “+ Create new secret key”.
   2. Give it a name you will recognise, such as DampApp Pro on my iPhone.
   3. Leave “Permissions” on “All”. The Restricted and Read only options can stop the app from using the AI.
   4. Confirm to create it, then copy the key straight away. OpenAI shows the full key only once.

   Lost the key before you pasted it?

   No problem. Delete it with the bin icon on the API keys page and create another. Keys are free to make and delete.

6. 6

   Step 6: Paste the key into DampApp Pro

   On your phone or tablet, open DampApp Pro and go to SettingsIntegrations. Settings is the gear at the bottom right of the home screen.

   1. Under “AI Provider”, tap “OpenAI”.
   2. Tap the “OpenAI API Key” box and paste your key. It starts with sk- and is very long. Tap the eye icon to check it pasted in full, with no space at the end.
   3. Scroll down and tap “Save & Sync Settings”.

   

   

   

   The Integrations tab shows these boxes to Pro subscribers. If you are signed in, saving also keeps the key in your secure cloud profile, so it follows you to your other devices.

7. 7

   Step 7: Leave the model on Automatic

   After you paste a key, an “OpenAI Model” list appears under it. Leave it on the first option, “Automatic”. The app then picks OpenAI's newest low-cost model, which is fast, good at survey wording and one of the cheapest.

   You can choose a bigger model from the list, but it will cost more per request and is rarely better for report wording.

8. 8

   Step 8: Check it works

   Open any survey, type a rough note into a text box that has an “AI Polish” button (for example “damp patch by back door, plaster blown”), then tap “AI Polish”. It has a sparkle icon. If the note comes back rewritten, you are done. You will not see the app's daily AI limit again while your key is saved.

   If you see a message instead, look it up in If something goes wrong below.

OpenAI charges by the amount of text and pictures it reads and writes. For GPT-5.4 mini, which the app has picked automatically so far, our estimates are:

These are our estimates from OpenAI's published prices for GPT-5.4 mini (US$0.75 per million word-pieces read, US$4.50 per million written) and typical survey use. From app version 1.10.24, Automatic picks GPT-6 Luna, which OpenAI prices lower (US$0.10 and US$0.50), so treat these figures as the most you should expect. Your real figures are on OpenAI's Usage page (opens in a new tab).

Your key is like a card number for your OpenAI account: anyone who has it can spend your credit.

• Never post it online, put it in an email to someone else, or share a screenshot that shows it.
• DampApp Pro support will never ask you for your key.
• If you think someone else has it, delete it on the API keys page. OpenAI says deleted keys stop working within seconds. Then create a new one and paste that into the app.
• OpenAI switches off keys it finds published on the internet, which is another reason never to post one.